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VII. — Discoveiy of Jupiter's Satelites — Kepler — 
Sizzi — Astrologers — Maestlin — Horkey — 
Mayer. - - - - 84 

yill. — Observations on the Moon — Nebulae — Saturn — 

Venus — Mars - - - 104 

IX. — Account of the Academy at Lincea — Del Cim- 

ento — Royal Society. - - 114 

X. — Spots on the Sun — Essay on Floating Bodies — 

Scheiner — Change in Saturn. - 123 
XI. — Letter to Christina, Arch-Duchess of Tusca- 
ny — Caccini Galileo re-visits Rome 

Inchaffer — Problem of Longitudes. 142 

XII. — Controversy on Comets — Saggiatore — Galileo's 

reception by Urban VIII — His Family. 168 

XIII.— Publication of Galileo's System of the World— 

His condemnation and Abjuration. 16/ 

XIV. — Extracts from the Dialogues on the System. 196 
XV. — Galileo at Arcetri — Becomes Blind — Moon's 
Libration. — Publication of the Dialogues 
on Motion. „ _ _ 222 

XVI.— State of the Science of Motion before Galileo. 232 
XVII.— Galileo's Theory of Motion— Extracts from 

the Dialogues. - - - 248 

XVIII. — Correspondence on Longitudes — Pendulum 

Clock. _ - - - 274 

XIX. — Character of Galileo — Miscellaneous details — 

His Death— Conclusion. - 291 


We cannot duly appreciate our present facilities for acquiring knowledge 
and putting it to use, but by a faithful comparison with those of our prede- 
cessors in former generations. This is one principal purpose of history 
and biography. We need them, not exclusively to contribute to our enter- 
tainment, or to fill up our storehouse of information; but most of all, to 
help us estimate our own advantages, and employ them more efficiently for 
our own benefit, and that of coming generations. These remarks apply to 
every important subject, and to every class of community . The Christian — 
and who in this country is not a christian, at least in speculative assent to 
divine tnithl — a Christian can scarcely know the value of his faith, or the 
duties of his vocation, or the import of his profession, without looking from 
the hill of meridian light where Providence has placed him, into the retiring 
darkness. He must survey the total night of Paganism, the dim light of 
Judaism, and the gross mingling of darkness with light in a political and 
corrupt Christianity. Else he can scarcely know that he dwells in the light 
and is bound to be indeed a child of light. Among us, every man is born to 
be a practical politician, one of the sovereigns of the realm. But no one 
can estimate his birth-right as a free-man, or be an intelligent and useful 
republican, without some theoretic knowledge of the operations of despot- 
ism, and the miseries of degradation and servitude. The same is true of 
the pursuits of literature. We must look back to the time when there were 
no classic authors, no schools, and no art of printing: when the records of 
history, the productions of the bard, and all diat we now esteem as classical 
and refined, were secluded in cloisters from all profane eyes- 
rOn the attainments of our age in the sciences, however, a knowledge of 
the past throws a peculiar radiance. Our facilities for acquiring this kind of 
knowledge are so abundant, and are plBced so liberally within the reach of 
all classes, that we are entirely unconscious of the toils and struggles of 


those, whose labors we are constantly reaping. We riot in a profiision of 
fruits, on the culture of which we have bestowed no care. The results of 
numerous experunents have become common property. Long-cherished the- 
ories have been exploded by the light of truth. The principles of investi- 
gation have become known and established. An apparatus for the learner 
and the professor, is as familiar as the tools of the mechanic. But all this 
was not acquired in a day, nor yet in a century. Genius wrought out in- 
ventions and made discoveries, without precedents, without tools or helpers ; 
and against the combined power of ignorance [and self-interest, accredited 
them with the world. 

Galileo was one of the most distinguished among the pioneers of science. 
His name, and slight portions of his history, are familiar to all. This is not 
sufficient. His labors and their results should be well pondered and under- 
stood. He is entitled to this distinction, whether we consider the acumen, 
diligence and perseverance of the man; the importance of his discoveries; 
their influence on the extension of knowledge and the science of investiga- 
tion ; or the unfavorable period in whiph he lived, and the mountain diffi- 
culties with which he contended. To establish his claims to the attention 
of every American student, we need only notice his principal discoveries i 
which may be seen at a glance in the table of contents. These were made 
at a time, when the least innovation on received principles was sure to in- 
cur, both the odium of the populace and the persecutions of the Romish hie- 
rachy. Yet this profound philosopher, confident in his principles as based 
on incontrovertible facts, braved all discouragements and dangers, and be- 
queathed his discoveries and his fame as a precious legacy to succeeding 

This brief and comprehensive account of the distinguished Italian, was 
prepared in England, for the Library of Useful Knowledge, and is now 
published separately for more general use. 




The knowledge which we at present possess of the 
phenomena of nature and of their connection, has not 
by any means been regularly progressive, as we might 
have expected, from the time when they first drew 
the attention of mankind. Without entering into the 
question touching the scientific acquirements of east- 
ern nations at a remote period, it is certain that some 
among the early Greeks were in possession of several 
truths, however acquired, connected with the econo- 
my of the universe, which were afterwards sufi'ered to 
fall into neglect and oblivion. But the philosophers 
of the old school appear in general to, have confined 
themselves at the best to observations ; very few tra- 
ces remain of their having instituted experiments^ 
properly so called. This putting of nature to the tor- 



ture, as Bacon calls it, has occasioned the principal 
part of modern philosophical discoveries. The ex- 
perimentalist may so order his examination of nature 
as to vary at pleasure the circumstances in which it is 
made, often to discard accidents which complicate the 
general appearances, and at once to bring any theory 
which he may form to a decisive test. The province 
of the mere observer is necessarily limited ; the pow- 
er of selection among the phenomena to be presented 
is in great measure denied to him, and he may con- 
sider himself fortunate if they are such as to lead him 
readily to a knowledge of the laws which they follow. 
Perhaps to this imperfection of method it may be 
attributed that Natural Philosophy continued to be 
stationary, or even to decline, during a long series of 
ages, until little more than two centuries ago. With- 
in this comparatively short period it has rapidly 
reached a degree of perfection so different from its 
former degraded state, that we can hardly institute 
any comparison between the two. Before that epoch, 
a few insulated facts, such as might first happen to 
be noticed, often inaccurately observed, and always 
too hastily generalized, were found sufficient to ex- 
cite the naturalist's lively imagination ; and having 
once pleased his fancy with the supposed fitness of 
his artificial scheme, his perverted ingenuity was 
thenceforward employed in forcing the observed phe- 
nomena into an imaginary agreement with the result 
of his theory ; instead of taking the more rational, 
and it should seem, the more obvious, method of cor- 
Tecting the theory by the result of his observations, 


and considering the one merely as the general and ab- 
breviated expression of the other. But natural phe- 
nomena were not then valued on their own account, 
and for the proofs which they afford of a vast and be- 
neficent design in the structure of the universe, so 
much as for the fertile topics which the favorite mode 
of viewing the subject supplied to the spirit of scho- 
lastic disputation : and it is a humiliating reflection, 
that mankind never reasoned so ill as when they most 
professed to cultivate the art of reasoning However 
specious the objects, and alluring the announcements 
of this art, the then prevailing manner of studying it 
curbed and corrupted all that is free and noble in the 
human mind. Innumerable fallacies lurked every- 
where among the most generally received opinions, 
and crowds of dogmatic and self-sufficient pedants 
fully justified the lively definition, that ^^ logic is the 
art of talking unintelligibly on things of which we 
are ignorant.'' "^ 

The error which lay at the root of the philosophy 
of the middle ages was this : — from the belief that 
general laws and universal principles might be dis- 
covered, of which the natural phenomena were ef- 
fects, it was thought that the proper order of study 
was, first to detect the general cause, and then to pur- 
sue it into its consequences ; it was considered absurd 
to begin with the effect instead of the cause ; where- 
as the real choice lay between proceeding from par- 
ticular facts to general facts, or from general facts to 
particular facts ; and it was under this misrepresent- 
* Menage 


ation of the real question that all the sophistry lurk- 
ed. As soon as it is well understood that the general 
cause is no other than a single fact, common to a 
great number of phenomena, it is necessarily perceiv- 
ed that an accurate scrutiny of these latter must pre- 
cede any safe reasoning with respect to the former. 
But at the time of which we are speaking, those who 
adopted this order of reasoning^ and who began their 
inquiries by a minute and seduSipus investigation of 
facts, were treated with disdain, as men who degraded 
the lofty name of philosophy by bestowing it upon 
mere mechanical operations. Among the earliest and 
noblest of these w^as Galileo. 

It is common, especially in Great Britain, to name 
Bacon as the founder of the present school of experi- 
mental philosophy ; v/e speak of the Baconian or in- 
ductive method o/ reasoning as synonymous and con- 
vertible terms ; and we are apt to overlook what Ga- 
lileo had already done before Bacon's writings ap- 
peared. Certainly the Italian did not range over the 
circle of the sciences with the supreme and searching 
glance of the English philosopher, but v;e find in ev- 
ery part of his vrritings philosophical maxims, vvhich 
do not lose by comparison with those of Bacon: and 
Galileo deserves the additional praise, that he himself 
gave to the w^orld a splendid practical illustration of 
the value of the principles which he constantly re- 
commended. In support of this viev/ of the compara- 
tive deserts of these two celebrated men, we are able 
to adduce the authority of Hump, who will be readily 
admitted as a competent judge of philosophical merit, 


where his prejudices cannot bias his decision. Dis- 
cussing the character of Bacon, he says, — ^' If we 
consider the variety of talent displayed by this man, 
as a public spejiker, a man of business, a wit, a cour- 
tier, a companion, an author, a philosopher, he is 
justly the object of great admiration. If we consider 
him merely as an author and philosopher, the light in 
which we view him at present, though very estima- 
ble, he was yet inferior to his contemporary, Galileo, 
perhaps even to Kepler. Bacon pointed out at a 
distance the road to true philosophy : Galileo both 
pointed it out to others, and made himself considera- 
ble advances in it. The Englishman was ignorant of 
geometry : the Florentine revived that science, ex- 
celled in it, and was the first that applied it, together 
with experiment, to natural philosophy. The former 
rejected with the most positive disdain the system of 
Copernicus : the latter fortified it Va ith new proofs 
derived both from reason and the senses."^ 

If we compare them from another point of view, 
not so much' in respect of their intrinsic merit, as of 
the influence which each exercised on the philosophy 
of his age, Galileo's superior talent or better fortune, 
in arresting the attention of his contemporaries, seems 
indisputable. The fate of the two writers is directly 
opposed the one to the other ; Bacon's works seem 
to be most studied and appreciated when his readers 
have come to their perusal, imbued with knowledge 
and a philosophical spirit, which, however, they had 

* Hume's England, James I. 
B 2 


attained independently of his assistance. The proud \ 
appeal to posterity which he uttered in his will, — j 
^' For my naaie and memory, I leave it to men's 
charitable speeches, and to foreign nations, and the 
next ages,"— of itself indicates a consciousness of the ■ 
fact that his contemporary countrymen were but i 
slightly affected by his philosophical precepts. But | 
Galileo's personal exertions changed the general cha- 
racter of philosophy in Italy : at the time of his | 
death, his immediate pupils had obtained possession .| 
of the most celebrated universities, and were busily I 
engaged in practising and enforcing the lessons which 
he had taught them ; nor was it then easy to find i 
there a single student of natural philosophy who did ■ 
not readily ascribe the formation of his principles to ' 
the direct or remote influence of Galileo's example. 
Unlike Bacon's, his reputation, and the value of his ; 
writings, were higher among his contemporaries than ] 
they have since become. This judgment perhaps ^ 
awards the highest intellectual prize to him whose j 
disregarded services rise in estimation with the ad- ,| 
vance of knowledge ; but the praise due to superior I 
usefulness belongs to him w^io succeeded in training | 
round him a school of imitators, and thereby enabled , 
his imitators to surpass himself. | 

The biography of men who have devoted them- j 
selves to philosophical pursuits seldom affords so va- : 
rious and striking: a succession of incidents as that of i 
a soldier or statesman. The life of a man who is \ 
shut up during the greater part of his time in his i 
study or laboratory supplies but scanty materials for ! 


personal details : and the lapse of time rapidly re- 
moves from us the opportunities of preserving such 
peculiarities as might have been worth recording. An 
account of it will therefore consist chiefly in a review 
of his works and opinions, and of the influence which 
he and they have exercised over his own and succeed- 
ing ages. Vievs'ed in this light, few lives can be con- 
sidered more interesting than that of Galileo; and if 
we compare the state in which he found, with that in 
which he left, the study of nature, we shall feel how 
justly an enthusiastic panegyric pronounced upon the 
age immediately following him may be transferred to 
this earlier period. '-This is the age wherein all 
men's minds are in a kind of fermentation, and the 
spirit of wisdom and learning begins to mount and 
free itself from those drossy and terrene impediments 
wherevrith it has been so long clogged, and from the 
insipid phlegm and caput mortuum of useless notions 
in which it hath endured so violent and long a fixa- 
tion. This is the age wherein, methinl^, philosophy 
comes in with a spring tide, and the peripatetics may 
as well hope to stop the current of the tide, or, vrith 
Xerxes, to fetter the ocean, as hinder the overflow- 
ing of free philosophy. Methinks I see how all the 
old rubbish must be thrown away, and the rotten 
buildings be overthrown and carried away, with so 
powerful an inundation. These are the days that 
must lay a new foundation of a magnificent philoso- 
phy, never to be overthrov^'n, that will empirically 
and sensibly canvass the phenomena of nature, dedu- 
cing the causes of things from such originals in na- 


ture as we observe are producible by art, and the in- 
fallible demonstration of mechanics : and certainly 
this is the way, and no other, to build a true and per- 
manent philosophy."^ 


Galileo's Bhih — Family — Education — Observation of the Peii- 
didum — Pulsilogies — Hydrostatical Balance — Lecturer at 

Galileo Galilei was born at Pisa, on the 15th day 
of February, 1564, of a noble and ancient Floren- 
tine family, which, in the middle of the fourteenth 
century, adopted this surname instead of Bonajuti, 
under which several of their ancestors filled distin- 
guished offices in the Florentine state. Some misap- 
prehension has occasionally existed, in consequence 
of the identity of his proper name with that of his 
family. His most correct appellation would perhaps 
be Gahleo de' Galilei : but his surname usuallv oc- 
curs as we have written it. He is most commonly 
spoken of by his Christian name, agreeably to the 
Italian custom ; just as Sanzio, Buonarotti, Sarpi, 
Reni, Vecelli, are universally known by their Chris- 
tian names of Raphael, Michel Angelo, Fra Paolo, 
Guido, and Titian. 

* Power's Experimental Philosophy, 1663. 


Several authors have followed Rossi in styling Ga- 
lileo illegitimate, but without having any probable 
grounds even when they wrote ; and the assertion has 
since been completely disproved by an inspection of 
the registers at, Pisa and Florence, in which are pre- 
served the dates of his birth, and of his mother's mar- 
riage, eighteen months previous to it. 

His father, Vincenzo Galilei, was a man of consid- 
erable talent and learning, vdth a competent know- 
ledge of mathematics, and particularly devoted to the 
theory and practice of music, on which he published 
several esteemed treatises. The only one which it is 
at present easy to procure — his Dialogue on Ancient 
and Modern Music — exhibits proofs, not only of a 
thorough acquaintance with his subject, but of a 
sound and vigorous understanding applied to other 
topics incidentally discussed. There is a passage in 
the introductory part, which becomes interesting 
when considered as affording some traces of the pre- 
cepts by which Galileo was in all probability trained to 
reach his preeminent station in the intellectual world. 
^' It appears to me,'' says one of the speakers in the 
dialogue, •* that they who in proof of any assertion 
rely simply on the weight of authority, without addu- 
cing any argument in support of it, act very absurd- 
ly : I, on the contrary, wish to be allovv'ed freely to 
question and freely to answer you without any sort of 
adulation, as well becomes those who are truly in 
search of truth." Sentiments like these vrere of rare 
occurrence at the close of the sixteenth century, and 
it is to be regretted that Yincenzo hardly lived long 


enough to witness his idea of a true philosopher i 
splendidly realized in the person of his son. Vincen- | 
zo died at an advanced age, in 1591. His family , 
consisted of three sons, Galileo, Michel Angelo, and I 
Benedetto, and the same number of daughters, Giu- j 
lia, Virginia, and Livia. After Vincenzo's death the '| 
chief support of the family devolved upon Galileo, ; 
who seems to have assisted them to his utmost pow- 
er. In a letter to his mother, dated 1600, relative to | 
the intended marriage of his sister Livia with a cer- | 
tain Pompeo Baldi, he agrees to the match, but re- j 
commends its temporary postponement, as he was at ! 
that time exerting himself to furnish money to his | 
brother Michel Angelo, who had received the offer \ 
of an advantageous settlement in Poland. As the ^ 
sum advanced to his brother, which prevented him 
from promoting his sister's marriage, did not exceed '•• 
200 crowns, it may be inferred that the family were j 
in a somewhat straii^ed Gondition. However, he I 
promises, as soon as his brother should repay him, ■ 
^^to take measures for the young lady, since she too 1 
is bent upon coming out to prove the miseries of this 
world." — As Livia was at the date of this letter in a ! 
convent, the last expression seems to denote that she , 
had been destined to take the veil. This proposed t 
marriage never took place, but Livia was afterwards 
married to Taddeo Galletti : her sister Virginia mar- j 
ried Benedetto Landucci. Galileo mentions one of 
his sisters, (without naming her,) as living with him I 
in 1619 at Bellosguardo. Michel Angelo is probably 
the same brother of Galileo who is mentioned by Li- ' 


ceti as having communicated from Germany some ob- 
servations on natural history.*" He finally settled in 
the service of the Elector of Bavaria; in what situ- 
ation is not known, but upon his death the Elector 
granted a pension to his family, who then took up 
their abode at Munich. On the taking of that city 
in 1636, in the course of the bloody thirty year's 
war, which was then raging between the Austriairs 
and Swedes, his widow and four of his children were 
killed, and every thing which they possessed was 
either burnt or carried away. Galileo sent for his 
two nephews, Alberto and a younger brother, to Ar- 
cetri, near Florence, where he was then living. These 
two were then the only survivors of Michel Angelo's 
family ; and many of Galileo's letters about that date 
contain allusions to the assistance he had been af- 
fording them. The last trace of Alberto is on his re- 
turn into Germany to the Elector, in whose service 
his father had died. These details include almost 
every thing which is known of the rest of Vincenzo's 

Galileo exhibited early symptoms of an active and 
intelligent mind, and distinguished himself in his 
childhood by his skill in the construction of ingenious 
toys and models of machinery, supplying the deficien- 
cies of his information from the resources of his own 
invention ; and he conciliated the universal good will 
of his companions by the ready good nature with 
which he employed himself in their service and for 
their amusement. It is worthy of observation, that 

* De his quae diu vivunt. Patavii, 1612. 


the boyhood of his great follower, Newton, whose 
genius in many respects so closely resembled his own, 
was marked by a similar talent. Galileo's father was 
not opulent, as has been already stated : he was bur- 
dened with a large family, and was unable to provide 
expensive instructors for his son : but Galileo's own 
energetic industry rapidly supplied the want of better 
opportunities ; and he acquired, under considerable 
disadvantages, the ordinary rudiments of a classical 
education, and a competent knowledge of the other 
branches of literature which were then usually stud- 
ied. His leisure hours were applied to music and 
drawing : for the former accomplishment he inherited 
his father's talent, being an excellent performer on 
several instruments, especially on the rute ; this con- 
tinued to be a favorite recreation during the whole of 
his life. He was also passionately fond of painting, 
and at one time he wished to make it his profession : 
and his skill and judgment of pictures were highly 
esteemed by the most eminent contemporary artists, 
who did not scruple to ov>'n publicly their deference 
to young Galileo's criticism. 

When he had reached his nineteenth year, his fath- 
er, becoming daily more sensible of his superior gen- 
ius, determined, although at a great personal sacrifice, 
to give him the advantages of an university education. 
Accordingly, in 1581, he commenced his academical 
studies in the university of his native town, Pisa, his 
father at this time intending that he should adopt the 
profession of medicine. His instructor was the cele- 
brated botanist, Andreas Csesalpinus, who was profes- 


sor of medicine at Pisa, from 1567 to 1592. In the 
matriculation lists at Pisa, he is styled Galileo, the son 
of Vincenzo Galilei, a Florentine, Scholar in Arts. It 
is dated 5th November, 1581. Viviani, his pupil, 
friend, and panegyrist, declares that, almost from the first 
day of his being enrolled on the lists of the academy, 
he was noticed for the reluctance with which he hsten- 
ed to the dogmas of the Aristotelian philosophy, then 
universally taught ; and he scon becaiPiC obnoxious to 
the professors from the boldness with which he promul- 
gated what they styled his pliilosophical paradoxes. 
His early habits of free inquiry were irreconcileable with 
the mental quietude of his instructors, whose philosophic 
doubts, when they ventured to entertain any, vxre speed- 
ily lulled by a quotation from Aiistotle. Gahleo thought 
himself capable of giving the world an example of a 
sounder and more original mode of thinking ; he felt 
himself destined to be the founder of a new school of 
rational and experimental philosophy. Of this we are 
now seciu-ely enjoying the benefits ; and it is difficult at 
this time fully to appreciate the obstacles which then 
presented themselves to free inquiry : but we shall see 
in the course of this narrative, how arduous their strug- 
gles were who happily effected this important revolution. 
The vindictive rancor with which the paitisans of the 
old philosophy never ceased to assail Galileo, is of it- 
self a sufficient proof of the prominent station which 
he occupied in the contest. 

Galileo's eai'hest mechanical discovery, to the superfi- 
cial observer, apparently an imimportant one, occurred 
diu'ing the period of liis studies at Pisa, His attention 


was one day arrested by the vibrations of a lamp swing- 
ing from the roof of the cathedral, which, whether great 
or small, seemed to recur at equal interv^als. The in- 
struments then employed for measuring time were very 
imperfect : Galileo attempted to bring his observation 
to the test before quitting the church, by comparing 
the vibrations with the beatings of his own pulse, and 
his mind being then principally employed upon his in- 
tended profession, it occurred to him, when he had 
further satisfied himself of their regularity by repeated 
and varied experiments, that the process he at first adopt- 
ed might be reversed, and that an instrument on this 
principle might be usefully employed in ascertaining 
the rate of the pulse, and its variation from day to day. 
He immediately carried the idea into execution, and it 
was for this sole and limited purpose that the first pen- 
dulum was constructed. Viviani tells us, that the value 
of the invention was rapidly appreciated by the physi- 
cians of the day, and was in common use in 1653, when 
he wrote. 

Santorio, who was professor of medicine at Padua, 
has given representations of four different forms of these 
instruments, which he calls puls'HAgies, [pulsilogias^) and 
strongly recommends to medical practitioners. These 
instruments seem to have been used in the following 
manner. No. 1 consists merely of a weight fastened to 
a string and a graduated scale. The string being gather- 
ed up into the hand till the vibrations of the w^eight co- 
incided with the beatings of the patient's pulse, the 
length was ascertained from the scale, which, of course, 
if great, indicated a languid, if shorter, a more lively 



taction. In No. 2 the improvement is introduced of 
comiectmg the scale and string ; the length of the latter 
is regulated by tlie turns of a peg at a, and a bead upon 
the string at i, showed the measure. No. 3 is still 
more compact, the string being shortened by winding 
upon an axle at the back of the dial plate. The con- 
struction of No. 4, which Santorio claims as his o\^'n 
improvement, is not given, but it is probable that the 
principal mdex, by its motion, shifted a weight to differ- 
ent distances from the point of suspension, and that the 
period of vibration was still more accurately adjusted by 
a smaller weight, connected with the second index. 
Venturi seems to have mistaken the third figure for that 
of a pendulum clock, as he mentions this as one of the 
earliest adaptations of Galileo's principle to that pur- 
pose ; but it is obvious, from Santorio's description, that 
it is nothmg more than a circular scale, the index show- 


ing, by the figure to ^vhich it points, the length of string 
remaining unwound from the axis. "We shall for the 
present, postpone the consideration of the invention of 
pendulum clocks, and the examination of the different 
claims to the honor of their first construction. 

At the time of which we are speaking, Galileo was 
entirely ignorant of mathematics, the study of which was 
then at a low" ebb, not only in Italy, but in every part of 
Europe. Commandine had recently revived a taste for 
the writings of Euclid and Archimedes, and Vieta Taita- 
lea and others had made considerable progress in algebra. 
Guido Ubaldi and Benedetti had dona sometliing towai'ds 
establishing the principles of statics, wliich was the only 
part of mechanics as yet cultivated ; bat with these in- 
considerable exceptions the appHcation of mathematics 
to the phenomena of natui'e vras scarcely thought of. 
Galileo's first inducement to acquire a knowledge of 
geometry ai'ose from his partiality for drawing and mu- 
sic, and from the wish to understand their principles and 
theory. His father, fearful lest he should relax liis med- 
ical studies, refused openly to encourage liim in tliis new 
pursuit ; but he comiived at the instruction which his 
son now began to receive in the writings of Euclid, from 
the tuition of an intimate friend, named Ostiho Ricci, 
who w^as one of the professors in the university. Gah- 
leo's W'hole attention w^as soon directed to the enjoyment 
of the new sensations thus commmiicated to him, inso- 
much that Vincenzo, finding his prognostics verified^ 
began to repent his indirect sanction, and privately re* 
quested Ricci to invent some excuse for discontinuing 
his lessons. But it was fortunately too late ; the in> 


pression was made and could not be effaced ; from that 
time Hippocrates and Galen lay unheeded before the 
young physician, and served only to conceal from his 
father's sight the mathematical volumes on which the 
whole of his time was really employed. His progress 
soon revealed the true nature of his pursuits : Vincenzo 
yielded to the irresistible predilection of his son's mind, 
and no longer attempted^ to turn him from the specula- 
tions to which his whole existence was thenceforward 

After mastering the elementary writers, Galileo pro- 
ceeded to the study of Archimedes, and, whilst perusing 
the Hydi'ostatics of that author, composed his earhest 
w^ork, — An Essay on the Hydrostatical Balance. In 
this he explains the method probably adopted by Ar- 
chimedes for the solution of Hiero's celebrated question, 
and shows himself already well acquainted with the true 
principles of specific gravities. This essay had an 
immediate and important influence on yomig Galileo's 
fortunes, for it introduced him to the approving notice 
of Guido Ubaldi, then one of the most distinguished 
mathematicians of Italy. At his suggestion Galileo ap- 
plied himself to consider the position of the centre of 
gravity in sohd bodies, a choice of subject that suffi- 
ciently showed the estimate Ubaldi had formed of his 
talents ; for it was a question on which Commandine 
had recently written, and w^hich engaged at that time tte 
attention of geometricians of the liighest order. Galileo 
tells us himself that he discontinued these researches on 
meeting with Lucas Valerie's treatise on the same sub- 
ject. Ubaldi was so much struck with the genius dis- 



played in the essay with which Galileo furnished him, 
tliat he introduced him to his brother, the Cai'dinal Del 
Monte. By this latter he was mentioned to Ferdinand 
de Medici, the reigning Duke of Tuscany, as a young 
man of whom the highest expectations might be enter- 
tained. By the Duke's patronage he was nominated, in 
1689, to the lectureship of mathematics at Pisa, being 
then in his twenty-sixth year. His pubhc salary was 
fixed at the insignificant sum of sixty crowns amiually, 
but he had an opportunity of greatly adding to his in- 
come by private tuition. 


Galileo at Pisa — Aristotle — Leonardo da Vinci — Galileo 
becomes a Copernican — Urstisins — Bruno — Experiments 
on falling bodies — Galileo at Padua — Thermometer, 

No sooner was Galileo settled in his new office than he re- 
newed his inquiries into the phenomena of nature with 
increased dihgence. He instituted a course of experi- 
ments for the purpose of putting to the test the mechan- 
ical doctrines of Aristotle, most of which he found un- 
supported even by the pretence of experience. It is to 
be regretted that we do not more frequently find detailed 
liis method of experimenting, than occasionally in the 


coiu'se of his dialogues, aiid it is chiefly upon the refer- 
ences which he makes to the resuhs with which the ex- 
periments furnished him, and upon the avowed and no- 
torious character of his pliilosophy, that the truth of these 
accounts must be made to depend. Yenturi has found 
several unpublished papers by Galileo on the subject of 
motion, in the Grand Duke's private library at Florence, 
bearing the date of 1590, in which are many of the 
tlieorems which he afterwards developed in his Dialogues 
on Motion. These were not pubhshed till fifty years 
afterwards, and we shall reserve an account of their con- 
tents till we reach that period of his life. 

Gahleo was by no means the first who had ventured 
to call in question the authority of Aristotle in matters of 
science, although he was undoubtedly the first whose 
opinions and writings produced a very marked and gen- 
eral effect. Nizzoli, a celebrated scholar who lived in the 
early part of the 16th century, had condemned x\iistotle's 
philosophy, especially his Physics, in very unequivocal 
and forcible terms, declaring that, although there were 
many excellent truths in his writings, the number was 
scarcely less of false, useless, and ridiculous proposi- 
tions. About the time of Galileo's birth, Benedetti 
had written expressly in confutation of several proposi- 
tions contained in Aristotle's Mechanics, and had ex- 
pounded in a clear manner some of the doctrines of 
statical equilibrium. Within the last forty years it has 
been estabUshed that the celebrated painter Leonardo da 
Vinci, w'ho died in 1519, amused Iris leisure houi^s in 
scientific pursuits; and many ideas appear to have oc- 
curred to him w^hich are to be found in the writings of 


Galileo at a later date. It is not impossible, (though 
tliere are probably no means of directly ascertaining the 
fact,) that Galileo may have been acquainted with Le- 
onardo's investigations, although they remained, till very 
lately, almost unknown to the mathematical world. This 
supposition is rendered more probable from the fact, 
that Mazenta, the preserver of Leonardo's manuscripts, 
was, at the very time of their discovery, a contemporary 
student with Galileo at Pisa. Kopernik, or as he is 
usually called, Copernicus, a native of Thorn in Prussia, 
had published his great work, De Revolutionibus, in 
1543, restoring the knowledge of the true theory of the 
smar system, and his opinions were gradually and silently 
gaining ground. "^ 

It is not satisfactorily ascertained at what period Gali- 
leo embraced the new astronomical theory. Gerard 
Voss attributes his conversion to a public lecture of 
Maestlin, the instructor of Kepler ; and later writers, 
among whom is Laplace, repeat the same story, but 
without referring to any additional sources of informa- 
tion, and in most instances merely transcribing Voss' 
words, so as to show indisputably whence they derived 
their account. Voss himself gives no authority, and his 
general inaccuracy makes his mere word not of much 
w^eight. The assertion appears, on many accounts, 
destitute of much probability. If the story were cor- 
rect, it seems likely that some degree of acquaintance, 
if not of friendly intercourse, would have subsisted 
between Maestlin and his supposed pupil, such as in fact 
we find subsisting between Msestlin and his acknowledged 
pupil Kepler, the devoted friend of Galileo; but, on the 


contrary, we find Msestlin vrriting to Kepler himself of 
Galileo as an entire stranger, and in the most disparaging 
terms. If Maestlin could lay claim to the honor of so 
celebrated a disciple, it is not hkely that he could fail so 
entirely to comprehend the distinction it must confer 
upon himself, as to attempt diminishing it by underrating 
his pupil's reputation. There is a passage in Galileo's 
works which more directly controverts the claim ad- 
vanced for Maestlin, although Salisbury in his hfe of 
Gahleo, having apparently an imperfect recollection of 
its tenor, refers to this very passage in confirmation of 
Yoss' statement. In the second part of the dialogue 
on the Copernican system, Galileo makes Sagredo, one 
of the speakers in it, give the following account: — '' Be- 
ing very young, and having scarcely finished my course 
of pliilosophy, which I left off as being set upon other 
employments, there chanced to come into these parts a 
certain foreigner of Rostoch, ichose 7iame^ as I remember j 
xoas Christianus Urstisius^ a follower of Copernicus^ 
who, in an academy, gave tvro or three lectures upon 
tliis point, to whom many flocked as auditors; but I^ 
thinking they went more for the novelty of the subject 
tlian otherwise, did not go to hear him ; for I had con- 
cluded with myself that that opinion could be no other 
than a solemn madness; and questioning some of those 
who had been there, J perceived they all made a jest 
thereof, except one, who told me that the business was 
not altogether to be laughed at : and because the man 
was reputed by me to be very intelligent and wary, I re- 
pented that I was not there, and began from that time 
forward, as oft as I met with any one of the Copernican 


^ persuasion, to demand of them if they had been always 
of the same judgment. Of as many as I exammed I 
found not so much as one who told me not that he had 
been a long time of the contraiy opinion, but to have 
changed it for this, as convinced by the strength of the 
reasons proving die same ; and afterwards questioning 
them one by one, to see whether they were well pos- 
sessed of the reasons of the other side, I found them all 
to be very ready and perfect in them, so that I could not 
truly say that they took this opinion out of ignorance, 
vanity, or to show the acuteness of their wits. On the 
contrary, of as many of the Peripatetics and Ptolemeans 
as I have asked, (and out of curiosity I have talked with 
many,) what pains they had taken in the book of Coper- 
nicus, I found very few that had so much as superficially 
perused it, but of those who I thought had imderstood 
the same, not one : and, moreover, I have inquired 
.amongst tlie followers of the Peripatetic doctrine, if ever 
any of them had held the contrary opinion, and hkewise 
found none that had. Whereupon, considering that 
there was no man who followed the opinion of Coperni- 
cus who had not been first on the contraiy side, and that 
was not very well acquainted with the reasons of Aris- 
totle and Ptolemy, and, on the contrary, that there w^as 
not one of the followers of Ptolemy that had ever been 
of the judgment of Copernicus, and had left that to 
embrace this of Aristotle; — considering, I say, these 
things, I began to think that one who leaveth an opinion 
imbued with his milk and followed by very many, to 
take up another, owned by very few, and denied by all 
the schools, and that really seems a great paradox, must 


needs have been moved, not to say forced, by more 
powerful reasons. For tliis cause I am become very 
curious to dive, as they say, into the bottom of this 
business." It seems improbable that Galileo should 
think it worth while to give so detailed an account of 
the birth and growth of opinion in any one besides 
himself; and although Sagredo is not the personage 
who generally in the dialogue represents Galileo, yet as 
the real Sagredo was a young nobleman, a pupil of 
Galileo himself, the account cannot refer to him. The 
circumstance mentioned of the intermission of his philo- 
sopliical studies, though in itself trivial, agrees very well 
with Galileo's original medical destination. Urstisius is 
not a fictitious name, as possibly Salisbury may have 
thought, when alluding to this passage; he was mathe- 
matical professor at Bale, about 1567, and several 
treatises by him are still extant. According to Kastner, 
his German name was Wursteisen. In 1568 Yoss informs 
us that he pubHshed some new questions on Pm^bach's 
Theory of the Planets. He died at Bale in 1586, when 
Gahleo was about twent}"-two years old. 

It is not unlikely that Gahleo also, in part, owed his 
emancipation from popular prejudices to the writings of 
Giordano Bruno, an unfortunate man, whose unsparing 
boldness in exposing fallacies and absurdities was re- 
warded by a judicial murder, and by the character of he- 
retic and infidel, with which liis executioners endeavored 
to stigmatize him for the purpose of covering over their 
own atrocious crime. Bruno was burnt at Rome in 
1600, but not,^as Montucla supposes, on account of his 
^' Spaccio della Bestia trionfante." The title of this 


book has led him to suppose that it was directed against 
the church of Rome, to which it does not in the shghtest 
tiegree relate. Bruno attacked the fashionable philoso- 
phy alternately with reason and ridicule, and numerous 
passages in his writings, tedious and obscure as they gen- 
erally are, show that he had completely outstripped the 
age in which he lived. Among his astronomical opin- 
ions, he believed that the universe consisted of innumer- 
able systems of suns with assemblages of planets revol- 
ving round each of them like our own earth, the small- 
ness of which, alone, prevented their being observed by 
us. He remarked further, ^' that it is by no means im- 
probable that there are yet other planets revolving round 
our own sun, which we have not yet noticed, either on 
account of their minute size or too remote distance from 
us." He declined asserting that all the apparently fixed 
stars are really so, considering this as not sufficiently pro- 
ved, '' because at such enormous distances the motions 
become difficult to estimate, and it is only by long ob- 
servation that we can determine if any of these move 
round each other, or what other motions they may have." 
He ridiculed the Aristotelians in no very measm'ed terms 
— ^' They harden themselves, and heat themselves, and 
embroil themselves for Aristotle ; they call themselves 
his champions, they hate all but Aristotle's friends, they 
ai^e ready to live and die for Aristotle, and yet they do 
not understand so much as the titles of Aristotle's chap- 
ters." And in another place he introduces an Aristote- 
lian inquiring, '^ Do you take Plato for an ignoramus — 
Aristotle for an ass ?" to whom he answers, '' My son, I 
neither call them asses, nor you mules, — them baboons, 


nor you apes, — as you would have me : I told you that 
I esteem them the heroes of the world, but I will not 
credit them without sufficient reason ; and if you were 
not both blind and deaf, you would understand that I 
must disbelieve their absurd and contradictory asser- 
tions." Bruno's works, though in general considered 
those of a visionary and madman, were in very extensive 
circulation, probably not the less eagerly sought after 
from being included among the books prohibited by the 
Romish church ; and although it has been reser\'ed for 
later observations to furnish complete verification of his 
most daring speculations, yet there was enough, abstract- 
edly taken, in the wild freedom of his remarks, to attract 
a mind like Galileo's ; and it is with more satisfaction 
that we refer the formation of his opinions to a man of 
undoubted though eccentric genius, like Bruno, than to 
such as Maestlin, who, though a diligent and careful ob- 
server, seems seldom to have taken any very enlarged 
views of the science on w^hich he was engaged. 

With a few exceptions similar to those above mention- 
ed, the rest of Galileo's contemporaries w^ell deserved 
the contemptuous epithet which he fixed on them of Pa- 
per Philosophers ; for, to use his own words, in a letter 
to Kepler on this subject, "- this sort of men fancied phi* 
losophy was to be studied like the jEneid or Odyssey, 
and that the true reading of nature was to be detected by 
the collation of texts. " Galileo's own method of philoso- 
phizing was widely different ; seldom omitting to bring 
with every new assertion the test of experiment either 
directly in confirmation of it, or tending to show its prob 
ability and consistency. We have already seen that he 


engaged in a series of experiments to investigate the truth 
of some of Aristotle's positions.' As fast as he succeeded 
in demonstrating the falsehood of any of them, he de- 
nounced them from his professorial chair with an energy 
and success which irritated more and more against him 
the other members of the academic body. 

There seems something in the stubborn opposition 
which he encountered in estabhshing the truth of his me- 
chanical theorems, still more stupidly absurd than in the 
ill will to which, at a later period of his life, his astro- 
nomical opinions exposed him : it is intelligible that the 
vulgar should withhold their assent from one who pre- 
tended to discoveries in the remote heavens, which few 
possessed instruments to verify, or talents to appreciate ; 
but it is difficult to find terms for stigmatizing the obdu- 
rate folly of those who preferred the evidence of their 
books to that of their senses, in judging of phenomena so 
obvious as those, for instance, presented by the fall of 
bodies to the ground. Aristotle had asserted, that if two 
different weights of the same material w^ere let fall from 
the same height, the heavier one would reach the ground 
sooner than the other, in the proportion of their weights. 
The experiment is certainly not a very difficult one, but 
nobody thought of that method of argument, and con- 
sequently this assertion had been long received, upon his 
word, among the axioms of the science of motion. Gali- 
leo ventured to appeal from the authority of Aristotle to 
that of his own senses, and maintained that, with the ex- 
ception of an inconsiderable difference, which he attrib- 
uted to the disproportionate resistance of the air, they 
would fall in the same time. The Aristotelians ridiculed 


and refused to listen to such an idea. Galileo repeated his 
experiments ifi their presence from the famous leaning 
tower of P^a: and with the sound of the simultaneously 
falling weights still ringing in their ears, they could persist 
in gravely maintaining that a weight of ten pounds would 
reach the ground in a tenth part of the time taken by one 
of a single pound, because they were able to quote 
chapter and verse in which Aristotle assures them that 
such is the fact. A temper of mind like this could not 
fail to produce ill will towards him who felt no scruples 
in exposing their wilful folly ; and the watcliful mahce 
of these men soon found the means of making Galileo de- 
sirous of quitting his situation at Pisa. Don Giovanni de' 
Medici, a natural son of Cosmo, who possessed a slight 
know^ledge of mechanics on which he prided himself, had 
proposed a contrivance for cleansing the port of Leghorn, 
on the efficiency of which Galileo was consulted. His 
opinion was unfavorable, and the violence of the inven- 
tor's disappointment, (for Galileo's judgment was verified 
by the result,) took the somewhat unreasonable direc- 
tion of hatred towards the man whose penetration had 
foreseen the failure. Galileo's situation was rendered so 
unpleasant by the machinations of this person, that he 
decided on accepting overtures elsewhere, which had 
already been made to him ; accordingly, under the ne- 
gotiation of his staunch friend Guido Ubaldi, and with 
the consent of Ferdinand, he procured from the repub- 
lic of Venice a nomination for six years to the profes- 
sorship of mathematics in the university of Padua, whith- 
er he removed in September 1592. 

Galileo's predecessor in the mathematical chair at Pa- 


duawas Moleti, who died in 1588, and the situation had 
remained unfilled during the intervening four years. This 
seems to show that the directors attributed but little im- 
portance to the knowledge which it w^as the professor's 
duty to impait. This inference is strengthened by the 
fact, that the amount of the annual salary attached to it 
did not exceed 180 florins, wliilst the professors of phi- 
losophy and civil law, in the same university, were 
rated at the annual stipends of 1400 and 1680 florins. Ga- 
lileo joined the miiversity about a year after its triumph 
over the Jesuits, who had established a school in Pa- 
dua about the year 1542, and, increasing yearly in influ- 
ence, had shown symptoms of design to get the whole 
management of the public education into the hands of 
their own body. After several violent disputes it was 
at length decreed by the Venetian senate, in 1591, that 
no Jesuit shoLild be allowed to give instruction at Padua 
in any of the sciences professed in the university. It 
does not appear that after this decree they were again 
troublesome to the university, but tliis first decree against 
tliem was followed, in 1606, by a second more peremp- 
tory, which banished them entirely from the Venetian 
territory. Galileo would of course find his fellow-pro- 
fessors much embittered against that society, and would 
naturally feel inclined to make common cause with them, 
so that it is not unlikely that the hatred which the Je- 
suits afterwards bore to Galileo on personal consider- 
ations, might be enforced by their recollection of the 
university to which he had belonged. 

Galileo's WTitings now began to follow^ each othej 
with great rapidity, but he was at this time appai^ejitlv 


SO careless of his reputation, that many of his works and 
inventions, after a long circulation in manuscript among 
his pupils and friends, found their way into the hands of 
those who were not ashamed to pubHsh them as their 
own, and to denounce Galileo's claim to the authorship 
as the pretence of an impudent plagiarist. He was, 
however, so much beloved and esteemed by his friends, 
that they vied with each other in resenting affronts of 
this nature offered to him, and in more than one instance 
he was reheved, by their full and triumphant answers 
from the trouble of vindicating his own character. 

To this epoch of Galileo's hfe may be referred his 
re-invention of the thermometer. The original idea of 
this useful instrument belongs to the Greek mathematician 
Hero ; and Santorio himself, who has been named as 
the inventor by Itahan writers, and at one time claimed 
it liimself, refers it to hmi. In 1638, Castelli wrote 
to Cesarmi that "^'he remembered an experiment sho^vn 
to him more than thirty-five years back by Galileo, who 
took a small glass bottle, about the size of a hen's egg, 
the neck of which was twenty -two inches long, and as 
narrow as a stravv\ Having well heated the bulb in his 
hands, and then introducing its mouth into a vessel in 
which was a Httle water, and withdrawing the heat of his 
hand from the bulb, the water rose in the neck of the 
bottle more than eleven inches above the level in the 
vessel, and Galileo employed this principle in the con- 
struction of an instrument for measuring heat and cold." 
In 1613, a Venetian nobleman named Sagredo, who has 
been already mentioned as Galileo's friend and pupil, 
WTites to him in the following words : '' I have brought 


the instrument which you invented for measuring heat 
into several convenient and perfect forms, so that the dif- 
ference of temperature between two rooms is seen as 
far as 100 degrees." This date is anterior to the claims 
both of Santorio and Drebbel, a Dutch physician, who 
was the first to introduce it into Holland. 

Galileo's thermometer, as we have just seen, consist- 
ed merely of a glass tube ending in a bulb, the air in 
which, being partly expelled by heat, was replaced by 
water from a glass into which the open end of the tube 
was plunged, and the different degrees of temperatm^e 
were indicated by the expansion of die air which yet 
remained in the bulb, so that the scale would be the re- 
verse of that of the thermometer now in use, for the 
water would stand at the highest level in the coldest wea- 
ther. If was, in truth, a barometer also, in consequence 
of the communication between the tube and external air, 
although Galileo did not intend it for this piu'pose, and 
when he attempted to determine the relative weight of 
the air, employed a contrivance still more imperfect than 
this rude bai^ometer would have been. A passage among 
his posthumous fragments intimates that he subsequent- 
ly used spirit of wine instead of water. 

Viviani attributes an improvement of this imperfect 
instrument, but without specifying its nature, to Ferdi- 
nand II. a pupil and subsequent patron of Galileo, and 
after the death of his father Cosmo, reigning duke of 
Florence. It was still further inproved by Ferdinand's 
younger brother, Leopold de Medici, who invented the 
modem process of expelling all the air from the tube by 
boihng the spirit of wine in it, and of hermetically sealing 


the end of the tube, whilst the contained liquor is in this 
expanded state, which deprived it of its barometrical ' 
character, and first made it an accurate thermometer. 
The final improvement was the employment of mercury 
instead of spirit of wine, w^hich is recommended by La- 
na so early as 1670, on account of its equable expan- 


Astronomy before Copernicus — Fracastoro — Bacon — Kep* 
ler — Galileo^s Treatise on the Sphere* 

This period of Galileo's lectureship at Padua derives 
interest from its including the first notice which we find 
of liis having embraced the doctrines of the Copernican 
astronomy. Most of our readers are aware of the prin- 
ciples of the theory of the celestial motions which Co- 
pernicus restored ; but the number of those who possess 
much knowledge of the cunib.rous and unwieldy system 
which it superseded, is perh^aps more limited. The 
present is not a fit opportunity to enter into many de- 
tails respecting it ; but a brief sketch of its leading 
principles is necessary to render what follows intel- 

The earth was supposed to be immovably fixed in 
the centre of the universe, and immediately surround- 


ing it the atmospheres of air and fire, beyond which the 
sun,- moon, and planets, were thought to be carried round 
the earth, fixed each to a seperate orb or heaven of sol- 
id but transparent matter. The order of distance in 
which they were supposed to be placed with regard to 
the central earth was as follows : The Moon, Mercur}^, 
Venus, the Sun, Mars, Jupiter, and Saturn. It be- 
came a question in the ages immediately preceding 
Copernicus, whether the Sun was not nearer the Earth 
than Mercury, or at least than Venus ; and this question 
was one on which the astronomical theorists were then 
chiefly divided. 

We possess at this time a curious record of a former 
belief in this arrangement of the Sun and planets, in the 
order in which the days of the week have been named 
from them. According to the dreams of Astrology, each 
planet was supposed to exert its influence in succession, 
reckoning from the most distant down to the nearest, 
over each hour of the twenty-four. The planet which 
was supposed to predominate over the first hour, gave 
its name to that day. The general reader will trace 
this curious fact more easily widi the French or Latin 
names than with the English, which have been translated 
into the titles of the corresponding Saxon deities. Pla- 
cing the Sun and planets in the following order, and begin- 
ning, for instance, with Monday, or the Moon's day ; Sat- 
urn ruled the second houi^ of that day, Jupiter the third, and 
so round till we come again and again to the Moon on 
the 8th, 15th and22d houi's ; Saturn ruled the 23d, Jupi- 
ter the 24th, so that the next day would be the day of 
Mars, or, as the Saxons translated it, Tuisco's day, or 


Tuesday. In the same manner the following days would 
belong respectively to Mercury or Woden, Jupiter or 
Thor, Venus or Frea, Saturn or Seater, the Sun, and 
again the Moon. In this manner the whole week will 
be found to complete the cycle of the seven planets. 

The other stars were supposed to be fixed in an outer 
orb, beyond which were two crystalline spheres, (as they 
were called,) and on die outside of all, the primum mobile 
or first movable^ which sphere was supposed to revolve 
round the earth in twenty-four hours, and by its friction, 
or rather, as most of the pliilosophers of that day chose 
to term it, by the sort of heavenly influence which it ex- 
ercised on the interior orbs, to carry them round with 
a similar motion. 

Hence the diversity of day and night. But beside 
this principal and general motion, each orb was sup- 
posed to have one of its own, which was intended to ac- 
count for the apparent changes of position of the plan- 
ets with respect to the fixed stars and to each other* 


This supposition, however, proving insufficient to ac- ; 
count for all the irregularities of motion observed, two | 
hypotheses were introduced. — First, that to each planet i 
belonged several concentric spheres or heavens, casing j 
each other like the coats of an onion, and secondly, that \ 
the centres of these solid spheres, with which the plan- I 
et revolved, were placed in the circumference of a sec- / 
ondary revolving sphere, the centre of which second- | 
ary sphere was situated at the earth. They thus ac- | 
quired the names of Eccentrics or Epicycles, the latter j 
word signifying a circle upon a circle. The whole | 
art of astronomers was then directed towards inventing » 
and combining different eccentric and epicyclical mo- i 
tions, so as to represent with tolerable fidelity the ever i 
varying phenomena of the heavens. Aristotle had lent | 
his powerful assistance in this, as in other branches of '' 
natural philosophy, in enabling the false system to pre- 
vail against and obliterate the laiowledge of the true, 
which, as we gather from liis own writings, was main- 
tained by some philosophers before his time: Of these 
ancient opinions, only a few traces now remain, principal- 
ly preserved in the works of those who were adverse to 
them. Archimedes says expressly that Aristarchus of 
Samos, who Uved about 300. B.C. taught the immobil- 
ity of the sun and stars, and that the earth is carried 
round the central sun.* Aristotle's words are; " Most of 

* The pretended translation by Rol^ervnJ of an Arr\l)ic version of Aris^ 
tai'cluis, " De Systemate Mundi," in which the Coj^rnican System is fully 
developed, is spurious. Menage asserts this in his observations on Diogen, 
Laert. lib. 8, sec. 85, torn, ii, p, 389. (Ed. Amst. 1692.) The commen- 
tary contains many authorities well worth consuking, Delambre, Histoirg 


those who assert that the whole corl^ave is finite, say 
that the earth is situated in the middle point of the uni- 
verse : those who are called Pythagoreans, who Uve in 
Italy, are of a contrary opinion. For they say that 
fire is in the centre, and that the earth, which, accord- 
ing to them, is one of the stars occasions the change of 
day and night by its own motion, with which it is carried 
about the centre." It might be doubtful, upon this pas- 
sage alone, whether the Pythagorean theory embraced 
more than the diurnal motion of the earth, but a little 
farther, we find the following passage : '^ Some as we 
have said make the earth to be one of the stars : others 
say that it is placed in the centime of the Universe, and 
revolves on a central axis." From which, in conjunction 
with the former extract, it very plainly appears that the 
Pythagoreans maintained both the diurnal and atmual 
motions the earth. 

de I'Astronomie, infers it from its not containing some opinions which Ar- 
chimides tells us were held by Aristarchus. A more direct proof may be 
gathered from the following blunder of the supposed translator. Astrono- 
mers had been long aware that the earth in diflferent parts of her orbits is at 
different distances from tlie sun. Roberval wished to claim for Aristarchus 
the credit of having known tliis, and introduced into his book, not only the 
mention of the fact, but an explanation of i|s cause. Accordingly, he makes 
Aristarchus give a reason " why the sun's aV)gee, (or place of greatest dis- 
tance from the earth,) must always be at the north summer solstice." In 
fact, it was there, or nearly so, in Robervars time, and he knew not but that 
it had always been there. It is however movable, and, when Aristarchus 
lived, was nearly half way between the solstices and equinoxes. He there- 
fore would hardly have given a reason for the necessity of a phenomenon of 
which, if he observed any thing on the subject, he must have observed the 
contrary. The change in the obliquity of tlie earth's axis to the ecliptic was 
known in the time of Roberval, and he accordingly has introduced the proper 
value which it had in Aristarchus' time. 


Some idea of the supeito)gatoiy labor entailed upon 
astronomers by the adoption of the system which places 
the earth in the centre, may be formed in a popular 
manner, by observing, in passing through a thickly 
planted wood, in how complicated a manner the rela- 
tive positions of the trees appear at each step to be 
continually changing, and by considering the difficulty 
with which the laws of their apparent motions could be 
traced, if we were to attempt to refer these changes to 
a real motion of the trees instead of the traveler. The 
apparent complexity in the heavens is still greater than in 
the case suggested ; because, in addition to the earth's mo- 
tions, with which all the stars appear to be impressed, 
each of the planets has also a real motion of its own, 
which of course greatly contributes to perplex and com- 
plicate the general appearances. Accordingly the hea- 
vens rapidly become, under this system, 

" With centric and eccentric scribbled o*er. 
Cycle and epicycle, orb in orb ;" 

crossing and penetrating each other in every direction. 
Maestlin has given a concise enumeration of the princi- 
pal orbs which belonged to this theory. After warning 
the readers that '^ they are not mere fictions which have 
nothing to correspond with them out of the imagination, 
but that they exist really, and bodily in the heavens," he 
describes seven principal spheres belonging to each plan- 
et, which he classes as Eccentrics, Epicycles, and Con- 
centrepicycles, and explains their use in accounting for 
the planet's revolutions, motions of the apogee, and 
nodes, &c. &c. In what manner this multitude of solid and 


crystalline orbs were secured from injuring or interfering 
with each other was not very closely inquired into. 

The reader will cease to expect any very intelligible 
explanation of this and numberless otlier difficulties which 
belong to this unwieldly machinery when he is introduced 
to the reasoning by which it was upheld. Gerolamo Fra- 
castoro, who hved in the 16th century, writes in the fol- 
lowing terms, in liis work entitled Homocentrica, (one of 
the best productions of the day,) in which he endeavors 
to simplify the necessary apparatus, and to explain all 
the phenomena (as the title of liis book impHes) by con- 
centric spheres round the eailh. '' There are some, not 
only of the ancients, but also among the moderns, who 
believe that the stars move freely without any such agen- 
cy ; but it is difficult to conceive in what mamier they 
have imbued themselves with this notion, since not only 
reason J but the very senses inform us that all the stag's are 
carried round fastened to solid spheres.''^ What ideas Fra- 
castoro entertained of the evidence of the ''senses" it is 
not now easy to guess ; but he goes on to give a speci- 
men of the ''reasoning" which appeai^ed to him so in- 
controvertible. " The planets are observed to move 
one wliile forwards, then backwards, now to the right, 
now to the left, quicker and slower by turns ; which 
variety is consistent with a compound structure like that 
of an animal wliich possesses in itself various springs 
and principles of action, but is totally at variance with 
our notion of a simple and undecaying substance like the 
heavens and heavenly bodies. For that which is simple 
is altogether single, and singleness is of one only nature, 
and one nature can be the cause of only one effect ; and 



therefore it is altogether impossible that the stars of them- 
selves should move with such variety of motion. And 
besides, if the stars move by themselves, they either 
move in an empty space, or in a fluid medium like the 
air. But there cannot be such a thing as empty space, 
and if there were such a medium, the motion of the 
star would occasion condensation and rarefaction in dif- 
ferent parts of it, which is the property of corruptible 
bodies, and where they exist some violent motion is 
gonig on ; but the heavens are incorruptible, and are 
not susceptible of violent motion, and hence, and from 
many other similar reasons, any one who is not obstinate 
may satisfy himself that the stars cannot have any inde- 
pendent motion." 

Some persons may perhaps think that arguments of 
this force are imnecessarily dragged from the obscuiity 
to which they are now for the most part happily consign- 
ed ; but it is essential, in order to set Galileo's character 
and merits in their true light, to show how low at this 
time philosophy had fallen. For we shall form a very 
inadequate notion of his powers and deserts if we do not 
contemplate him in the midst of men who, though of 
undoubted talent and ingenuity", could so far bewilder 
themselves as to mistake such a string of immeaning 
phrases for argument ; we must reflect on the difficulty 
every one experiences in delivering himself from the er- 
roneous impressions of infancy, which will remain stamp- 
ed upon the imagination in spite of all the efforts of 
matured reason to erase them, and consider every step 
of Galileo's course as a triumph over difficulties of a 
like nature. We ought to be fully penetrated with tliis 


feeling before we sit down to the perusal of his works, 
every line of which will then increase our admiration of 
the penetrating acuteness of his invention and unswerv'ing 
accuracy of his judgment. In almost every page we 
discover an allusion to some new experiment, or the 
germ of some new theory ; and amid all this wonderful 
fertihty it is rarely indeed that we find the exuberance of 
his imagination seducing him from the rigid path of phi- 
losophical induction. This is the more remarkable, as 
he was surrounded by friends and contemporaries of a 
different temperament and much less cautious disposition. 
A disadvantageous contrast is occasionally furnished even 
by the sagacious Bacon, who could so far deviate from 
the sound principles of inductive philosophy, as to \^Tite, 
for instance, in the following strain, bordering upon the 
worst manner of the Aristotehans : — '' Motion in a cir- 
cle has no limit, and seems to emanate from the appetite 
of the body, wliich moves only for the sake of n:ioving, 
and that it may follow itself and seek its ov>'n embraces, 
and put in action and enjoy its own natui'e, and exercise 
its peculiai' operation : on the contrary, motion in a 
straight line seems transitory, and to move towards a 
limit of cessation or rest, and that it may reach some 
point, and then put off its motion." Bacon rejected all 
the machinery of the primum mobile and the solid spheres, 
the eccentrics and the epicycles, and carried his dislike 
of these doctrines so fai' as to assert that nothing short 
of their gross absurdity could have driven theorists to 
the extravagant supposition of the motion of the earth, 
which, said he, 'Hve know to be most false." Instances 
of extravagant suppositions and premature generalizations 


are to be found in almost every page of his other great 
contemporary, Kepler. 

It is with pain that we observe Delambre taking every 
opportunity, in his admirable History of Astronomy, to 
undervalue and sneer at Galileo, seemingly for the sake 
of elevating the character of Kepler, who appears his 
principal favorite, but whose merits as a philosopher can 
not safely be brought into competition with that of his 
illustrious contemporary. Delambre is especially dissat- 
isfied with Galileo, for taking no notice, in his '' System 
of the World," of the celebrated laws of the planetary 
motions which Kepler discovered, and which are now 
inseparably connected with his name. The analysis of 
Newton and his successors has now identified those ap- 
parently mysterious laws with the general phenomena of 
motion, and has thus entitled them to an attention, of 
which, before that time, they were scarcely worthy ; at 
any rate, not more than is at present the empirical law 
w^hich includes the distances of all the planets from the 
sun (roughly taken) m one algebraical formiila. The 
observations of Kepler's day were scarcely accurate 
enough to prove that the relations which he discovered 
between the distances of the planets from the sim and 
the periods of their revolutions around him were neces- 
sarily to be received as demonstrated truths ; and Galileo 
surely acted most prudently and philosophically in hold- 
ing himself altogether aloof from Kepler's fanciful devices 
and numeral conciimities, although, with all the extrava- 
gance, they' possessed much of the genius of the Platon- 
ic reveries, and although it did happen that Galileo, by 
systematically avoiding them, failed to recognize son^e 


Important truths. Galileo, probably, was thinking of 
those very laws, when he said of Kepler, ''He possesses 
a bold and free genius, perhaps too much so ; but his 
mode of philosophizing is widely different from mine/' 
We shall have further occasion in the sequel to recog- 
nize the justice of tliis remai^k. 

In the treatise on the Sphere, which bears Gahleo's 
name, and which, if he be indeed the author of it, was 
composed duiing the early part of his residence at Padua, 
he also adopts the Ptolemaic system, placing the eailh 
himiovable in the centre, and adducing against its mo- 
tion tlie usual argimients, wliich in his subsequent wtI- 
tings he ridicules and refutes. Some doubts have been 
expressed of its authenticitj' ; but however tliis may be, 
we have it under Gahleo's own hand that he taught the 
Ptolemaic system, in compliance with popular preju- 
dices, for some time after he had privately become a 
convert to the conti'ary opinions. In a letter, appa- 
rently the first which he wrote to Kepler, dated from 
Padua, 1597, he says, acknowledging the receipt of Kep- 
ler's Mysterium Cosmograpliicmii, '' I have as yet read 
nothing beyond the preface of your bock, from which, 
however, I catch a glimpse of your meaning, and feel 
great joy on meeting with so powerful an associate in 
the pursuit of truth ; and consequently, such a friend to 
truth itself, for it is deplorable that there should be so 
few who care about truth, and who do not persist in 
their perverse mode of pliilosopliizing ; but as this is 
not the fit time for lamenting the melancholy condition 
of our times, but for congratulating you on your elegant 
discoveries in confirmation of the ti'uth, I shall only add 



a promise to peruse your book dispassionately, and ^\ ith 
a conviction that I shall find in it much to admire. 
This I shall do the more willingly because many years 
ago I became a convert to the opinions of Copernicus^ 
and by that theory have succeeded in fully explaining 
many phenomena, which on the contrary hypothesis are 
altogether inexplicable. I have arranged many argu- 
ments and confutations of the opposite opinions, which j 
however^ I have not yet dared to publish^ fearing the fate 
of our master Copernicus, wlio, although he has earned 
immortal fame among a few, yet by an infinite number 
(for so only can the number of fools be measm^ed) is ex- 
ploded and derided. If there were many such as you, I 
would venture to publish my speculations ; but since 
that is not so, I shall take time to consider of it." This 
interesting letter was the beginning of the friendship of 
these two great men, which lasted uninterruptedly till 
lG32,the date of Kepler's death. That extraordinary 
genius never omitted an opportunity of testifying his ad- 
miration of Galileo, although there were not wanting per- 
sons envious of their good understanding, who exerted 
themselves to provoke coolness and quarrel between 
them. Thus Brutius writes to Kepler in 1602 ; " Gali- 
leo tells me he has written to you, and has got your 
book, which however he denied to Magini, and I abused 
him for praising you with too many qualifications. I 
know it to be a fact, that both in his lectures, and else- 
where, he is publishing your inventions as his own ; but 
I have taken care, and shall continue to do so, that all 
this shall redound not to his credit but to yours." The 
only notice which Kepler took of these repeated insinua- 


tions, which appear to have been utterly groundless, was, 
by renewed expressions of respect and admiration, to 
testify the value he set upon his friend and fellow-laborer 
in philosophy. 


Galileo re-elected Professor at Padua — New Star — Coni' 
pass of Proportion — Capra — Gilbert — Proposals to 
return to Pisa — Lost Writings — Cavalieri, 

Galileo's reputation was now rapidly increasing: his 
lectures were attended by many persons of the highest 
rank ; among whom were the Archduke Ferdinand, af- 
terwards Emperor of Germany, the Landgrave of Hesse, 
and the Princes of Alsace and Mantua. On the expira- 
tion of the first period for which he had been elected 
professor, he was rechosen for a similar period, with a 
salary increased to 320 florins. The immediate occa- 
sion of this augmentation is said, by Fabroni, to have 
arisen out of the malice of an ill-wisher of Galileo, who, 
hoping to do him disservice, apprised the senate that he 
was not married to Marina Gamba, then living with him, 
and the mother of his son Vincenzo. TYliether or not 
the senate might consider themselves entitled to inquire 
into the morahty of his private Ufe, it was probably from 
a wish to mark their sense of the informer's imperti- 


nence, that they returned the brief answer, that ^'ifhe 
had a family to provide for, he stood the more in need of 
an increased stipend." 

During Galileo's residence at Padua, and, according 
to Viviani's intimation, towards the thirtieth year of his 
age, that is to say, in 1594, he experienced the first at- 
tack of a disease which pressed heavily on him for the 
rest of his life. He enjoyed, when a young man, a 
healthy and vigorous constitution, but chancing to sleep 
one afternoon near an open window, through which was 
blowing a current of air cooled ailificially by the fall of 
water, the consequences were most disastrous to him. 
He contracted a sort of chronic complaint, w^hich show- 
ed itself in acute pains in his limbs, chest, and back, ac- 
companied with frequent haemorrhages and loss of sleep 
and appetite ; and this painful disorder thenceforward 
never left him entirely, but recurred intermittingly, with 
greater or less violence, as^long as he lived. Others of 
the party did not even escape so well, but died shortly 
after committing this imprudence. 

In 1604, the attention of astronomers was called to 
the contemplation of a new star, which appeared sudden- 
ly with great splendor in the constellation Serpentarius, 
or Ophiuchus, as it is now more commonly called. 
Maesthn, who was one of the earhest to notice it, re- 
lates his observations in the following words: "How 
wonderful is this new star ! I am certain that I did not 
see it before the 29th of September, nor indeed, on ac- 
count of several cloudy nights, had I a good view till 
the 6th of October. Now that it is on the other side 
of the sun, instead of surpassing Jupiter as it did, and al- 
most rivalling Venus, it scarcely matches the Cor Leo- 


nis, and hardly surpasses Saturn. It continues, however, 
to shine with the same bright and strongly sparkling light, 
and changes its colors almost with every moment ; first 
tawny, then yellow, presently purple and red, and when 
it hafs risen above the vapors, most frequently white." 
Tliis was by no means an unprecedented phenomenon ; 
and the curious reader may find in RiccioH a catalogue 
of the principal new stars which have at diiferent times 
appeared. There is a tradition of a similar occurrence 
as early as the times of the Greek astronomer, Hippar- 
chus, who is said to have been stimulated by it to the 
formation of his catalogue of the stars ; and only thirty- 
tw^o years before, in 1572, the same remarkable phe- 
nomenon in the constellation Cassiopeia was mainly in- 
strumental in detacliing the celebrated Tycho Brahe 
from the chemical studies, which till then divided his at- 
tention with astronomy. Tycho's star disappeared at 
the end of two yeai's ; and at that time Galileo was a 
child. On the present occasion, he set himself earnestly 
to consider the new phenomenon, and embodied the re- 
sults of his observations in tliree lectiinres, which have 
been unfortunately lost. Only the exoroium of the first 
has been preserved ; in this he reproaches his auditors 
with their general insensibility to the magnificent won- 
ders of creation daily exposed to their view, in no re- 
spect less admirable than the new prodigy, to hear an 
explanation of which they had hurried in crowds to his 
lecture room. He showed, from the absence of paral- 
lax, that the new star could not be, as the vulgar hy- 
pothesis represented, a mere meteor engendered in our 
atmosphere and nearer the earth than the moon, but must 
be situated among the most remote heavenly bodies* 


This was inconceivable to the Aristotelians, whose no- 
tions of a perfect, simple, and unchangeable sky, were I 
quite at variance with the introduction of any such new ^ 
body ; and we may perhaps consider these lectures as 
the first pubhc declaration of Galileo's hostility to the 
old Ptolemaic and Aristotelian astronomy. 

In 1606 he was re-appointed to the lecturesliip, and i 
his salary a second time increased, being raised to 520 '\ 
florins. His public lectures were at this period so much \ 
tlironged that the ordinary place of meeting vvas found \ 
insufficient to contain his auditors, and he was on seve- 
ral occasions obhged to adjourn to the open air, — even \ 
from the school of medicine, which was calculated to \ 
contain one thousand persons. 

About this time he was considerably annoyed by a ■ 
y^oung .Milanese, of the name of Balthasar Capra, who 
pirated an instrument which Galileo had invented some '; 
years before, and had called the geometrical and military \ 
compass. The original offender was a German, named I 
Simon Mayer, whom we shall meet with afterwards ar- \ 
rogating to himself the merit of one of Galileo's astro- i 
nomical discoveries ; but on this occasion, as soon as he ^ 
found Galileo disposed to resent the injury done to him,, 
he hastily quitted Italy, leaving his friend Capra to bear i 
alone the shame of the exposure which followed. The? ; 
instrument is of simple construction, consisting merely^ - 
of two straight rulers, connected by a joint ; so that they : 
can be set to any required angle. This simple and use- 
ful instrument, now called the Sector, is to be found in \ 
almost every case of mathematical instruments. Instead \ 
of the trigonometrical and logarithmic lines which are j 
now generally engraved upon it, Galileo's compass mere* 1 



ly contaiiiecL on one side, three pairs of lines, divided in 
simple, duplicate, and triplicate proportion, ^vith a fourth 
pair on wliich were registered the specific gravities of 
several of the most common metals. These were used 
for multiphcations. divisions, and the extraction of roots ; 
for finding the dimensions of equally heavy balls of difl:er- 
ent materials, S:c. On the other side were lines con- 
trived for assisting to describe any required polya'on on a 
gi^^en line ; for finding polygons of one kind equal in area 
to those of another ; and a multhude of other similar op- 
erations useful to the practical engineer. 

Unless tlie instrument, wliich is now called Gunter's 
Scale, be muxh altered from what it originally was, it 
is difficuk to understand on what grounds Salisbury 
charges Gunter with plagiaiism from Galileo's Compass. 
He declares that he has closely compared the tvro, and 
can find no diSerence between them.* There has also 
been some confusion, by several \^Titers, between this 
instrument and what is now commonly called the Pro- 
portional Compass. The latter consists of two shps of 
metal pointed at each end. and connected by a pin vrhich, 
shding in a groove through both, can be shifted to dif- 
ferent positions. Its use is to find proportional lines ; 
for it is obvious that the openings measm^d by each pair 
of legs will be in the same proportion in wliich the slips are 
divided by the centre. The divisions usually mai'ked 
on it ai^e calculated for findmg the submultiples of straight 
lines, and the chords of sub multiple arcs. Montucla has 

* SalisbuiT alludes to the instinanient described and figm-ed in '•' The L'se 
of the Sector, Crosse Staffe? and other In5trumeut5. London^ 1624.'' It is 
exactly Galileo's Compass. 


Mentioned this mistake of one instrument for the other, 
knd charges Voltaire with the more inexcusable error of j 
confounding Galileo's with the Mariner's Compass. He i 
Refers to a treatise by Hulsius for his authority in at- i 
tributing the Proportional Compass to Burgi, a Swiss as- i 
tronomer of some celebrity. Horcher also has been | 
styled the inventor ; but he did no more than describe i 
its form and application. In the frontispiece of his book 
is an engraving of this compass exactly similar to those | 
ivhich are now used. To the description which Gahleo ' 
published of his compass, he added a short treatise on 
the method of measuring heights and distances with the 
quadrant and plumb hne. The treatise, wliich is printed ' 
by itself at the end of the first volume of the Padua ! 
edition of Galileo's works, contains nothing more than i 
die demonstrations belonging to the same operations. 
They are quite elementary, and contain little or nothing 
that was new even at that dme. 

Such an instrument as Galileo's Compass was of 
inuch more importance before the grand discovery of ] 
logaritlims than it can now be considered: however, 
it acquires an additional interest from the value- which I 
he himself set upon it. In the year 1607, Capra, at 
the instigation of Mayer, published as his own invention, 
what he calls the Proportional Hoop, which is a mere 
copy of Galileo's instrument. This produced from Galileo 
a long essay, entitled ''A Defense of Galileo against 
the Calumnies and Impostiu"es of Balthasar Capra." His ! 
principal complaint seems to have been of the misrepre- j 
sentations which Capra had published of his lectures on i 
the new star already mentioned, but he takes occasion, \ 


after pointing out the blunders and falsehoods which Capra 
had committed on that occasion, to add a complete proof 
of his piracy of the geometrical compass. He showed, 
from the authenticated depositions of workmen, and of 
those for whom the insti'uments had been fabricated, that 
he had devised them as early as tlie year 1597, and had 
explained their construction and use both to Balthasai' 
himself and to liis father Aurelio Capra, who was then 
residing in Padua. He gives, in the same essay, the 
minutes of a j^ubhc meeting between himself and Capra, 
in which he proved, to the satisfaction of the university, 
that wherever Capra had endeavored to introduce into 
his book propositions wliich were not to be met with in 
Galileo's, he had fallen into the greatest absurdities, and 
beti'ayed the most complete ignorance of liis subject. 
The consequence of this public exposure, and of the 
report of the famous Fra Paolo Sai'pi, to whom the 
matter had been referred, was a formal prohibition by 
the university of Capra's pubhcation, and all copies of 
the book then on hand were seized, and probably de- 
stroyed, though Galileo has preserved it from oblivion 
by incorporating it in his ovm pubhcation. 

Nearly at the same time, 1607, or immedktely after, 
he first turned his attention towai'ds the loac^^tone, on 
which our coLintrpiian Gilbert had already published liis 
researches, conducted in the true spirit of the inductive 
method. Very little that is original is to- be found in 
Galileo's works on tliis subject, except some allusion to liis 
method of arming magnets, in which, as in most of liis 
practical and mechanical operations, he appears to have 
been singularly successful. Sir Kenelm Digby asserts.. 


that the magnets armed by Galileo would support twice 
as great a weight as one of Gilbert's of the same size. 
Galileo was well acquainted, as appears from his frequent 
allusions in different parts of his works with what Gilbert 
had done, of w^hom he says, '' I extremely praise, ad- 
mire, and envy this author ; — I think him, moreover, 
worthy of the greatest praise for the many new and 
true observations that he has made to the disgrace of so 
many vain and fabling authors, who write, not from their 
own knowledge only, but repeat every thing they hear 
from the foohsh vulgar, without attempting to satisfy 
themselves of the same by experience, perhaps that they 
may not diminish the size of their books." 

Galileo's reputation being now greatly increased, pro- 
posals were made to him, in 1609, to return to his origi- 
nal situation at Pisa. He had been in the habit of 
passing over to Florence dm'ing the academic vacation, 
for the purpose of giving mathematical instruction to the 
younger members of Ferdinand's family ; and Cosmo, 
who had now succeeded his father as duke of Tuscany, 
regretted that so masterly a genius had been allowed 
to leave the university which he natui^ally should have 
graced. A few extracts from Galileo's answers to these 
overtures will serve to show the nature of his situation 
at Padua, and the manner in w^hich his time was there 
occupied. '* I will not hesitate to say, having now labor- 
ed during twenty years, and those the best of my life, in 
dealing out, as one may say, in detail, at the request of^ 
any body, the Uttle talent which God has granted to my 
assiduity in my profession, that my wish certainly would 
be to have sufficient rest and leisure to enable me, be-. 


fore my life comes to its close, to conclude three great 
works which I have in hand, and to pubUsh them ; which 
might perhaps bring some credit to me, and to those 
who had favored me in this undertaking, and possibly 
may be of greater and more frequent service to students 
than in the rest of my life I could personally afford 
them. Greater leisure than I have here I doubt if I 
could meet with elsewhere, so long as I am compelled 
to support my family from my public and private lec- 
tures, (nor would 1 willingly lecture in any other city 
than this, for several reasons which would be long to 
mention,) nevertheless not even the liberty I have here 
is sufficient, where I am obhged to spend many, and 
often the best hours of the day at the request of this and 
that man. — My public salary here is 520 florins, which 
I am almost certain will be advanced to as many crowns 
upon my re-election, and these I can greatly Increase by 
receiving pupils, and from private lectures, to any ex- 
tent that I please. My public duty does not confine 
me during more than 60 half hours in the yeai', and even 
that not so strictly but that I may, on occasion of any 
business, contrive to get some vacant days ; the rest of 
my time is absolutely at my own disposal ; but because 
my private lectures and domestic pupils are a great 
hindrance and interruption of my studies, 1 wish to hve 
entirely exempt from the former, and in great measure 
from the latter : for if I am to return to my native coun- 
try, I should wish the first object of his Serene High- 
ness to be, that leisure and opportunity should be given 
me to complete my works without employing myself in 
lecturing. — And, in short, I should wish to gain my bread 


from my writings, which I would ahvays dedicate to my 
Serene Master. — The works which I have to finish are i 
principally — two books on the system or structure of the 
Universe, an immense work, full of philosophy, astronomy, i 
and geometry; three books on Local Motion, a science \ 
entirely new, no one, either ancient or modern, having : 
discovered any of the very many admirable accidents i 
which I demonstrate in natural and violent motions, so • 
that I may with very great reason call it a new science, I 
and invented by me from its very first principles; three i 
books of Mechanics, two on the demonstration of prin- i 
ciples and one of problems; and although others have treat- 
ed this sam.e matter, yet all that has been hitherto writ- i 
ten, neither in quantity, nor otherwise, is the quarter of i 
what I am ^vriting on it. I have also different treatises I 
on natural subjects ; On sound and speech ; On Hght and < 
colors ; On the tide ; On the composition of continuous i 
quantity ; On the motions of animals ; — -And others be- « 
sides. I have also an idea of writing some books rela- i 
ting to the mihtary art, giving not only the model of a ] 
soldier, but teaching with very exact rules every thing \ 
which it is his duty to know, that appends upon mathe- i 
matics ; as the knowledge of castraii^tation, drawing up \ 
battahons, fortifications, assaults, planning, smweying, the 
knowledge of artillery , tlie use of instruments, &c. I 
also wish to reprint the ^ Use of my Geometrical Com- 
pass,' which IS dedicated to his higlmess, and which is 
no longer to be met with ; for.tliis instrument has expe- 
rienced such favor from the public, that in fact no other 
instruments of the same kind are now made, and I 
know that up to this time several thousands of mine have 


been made. — I say notliing as to the amount of my sala- 
ry, feeling convinced that as I am to live upon it, the 
graciousness of his highness would not deprive me of 
any of those comforts, which, however, I feel the want 
of less than many others; and therefore I say nothing more 
on the subject. Finally, on the title and profession of my 
service, I should wish that to the name of Mathematician, 
his highness would add that of Philosopher, as I profess 
to have studied a greater number of years in philosophy 
than months in pure mathematics; and how I have profit- 
ed by it, and if I can or ought to deserve this title, I 
may let their highnesses see as often as it shall please 
them to give me an opportunity of discussing such sub- 
jects in their presence with those who are most esteem- 
ed in this knowledge." It may perhaps be seen in the 
expressions of this letter, that Galileo was not incHned 
to undervalue his own merits, but the peculiar nature of 
the correspondence should be taken into the account;, 
which might justify his indulging a little more than usual 
in self-praise ; and it would have been perhaps ahnost 
impossible for him to have remained entirely blind to his 
vast superiority over his contemporaries. 

Many of the treatises which Galileo here mentions, as 
well as another on dialling, have been irrecoverably lost, 
through the superstitious weakness of some of his rela- 
tions, who, after his death, suffered the family confessor 
to examine his papers, and to destroy whatever seemed 
to him objectionable ; a portion, which, according to the 
notions then prevalent, was like to comprise llie most 
valuable part of his papers, submitted to this expArgation. 
It is also supposed that many were burnt by his infatu- 



ated grandson Cosimo, who conceived he was thus of- 
fering a proper and pious sacrifice before devoting him- 
self to the hfe of a missionaiy. A Treatise on Fortifi- 
cation, by Galileo, was foimd in 1793, and is contained 
among the documents published b}^ Venturi. Galileo 
does not profess in it to give much original matter, but 
to lay before liis readers a compendium of the most 
approved principles then ah^eady known. It has heen 
supposed that Gustavus Adolphus of Sweden attended 
Galileo's lectures on this subject, whilst in Italy ; but 
the fact is not satisfactorily ascertained. Galileo himself 
mentions a prince Gustavus of Sweden, to whom he 
gave instruction in mathematics, but the dates cannot 
well be made to agree. The question deserves notice 
only from its having been made the subject of contro- 

The loss of Galileo's essay on Continuous Quantity 
is particularly to be regretted, as it would be highly in- 
teresting to see how far he succeeded in methodizing his 
thoughts on this important topic. It is to liis pupil Cava- 
lieri (who refused to pubhsh his book so long as he hop- 
ed to see Gahleo's printed) that we owe ^^ The Method 
of Indivisibles," which is universally recognized as one 
of the first germs of the powerful methods of modern 
analysis. Throughout Gahleo's works we find many in- 
dications of liis having thought much on the subject, but 
his remarks are vague, and bear little, if at all, on the ap- 
pHcation of the method. To tliis the chief pait of Cava- 
lieri's book is devoted, though he was not so entirely re- 
gardless of the principles on which his method of meas- 
ing spaces is founded, as he is sometimes represented. 


This method consisted in considering lines as made up 
of an infinite number of points, surfaces in like manner 
as composed of lines, and solids of surfaces ; but there 
is an observation at the beginning of the 7th book, which 
shows cleai^ly that Cavaheri had taken a much more 
profound view of the subject than is imphed in tliis su- 
perficial exposition, and had approached very closely to 
the apparently more exact theories of his successors. 
Anticipating the objections to his hypothesis, he argues, 
that "^ there is no necessity to suppose the continuous 
quantities made up of these indivisible pails, but only 
that they icill observe the same ratios as those parts do,'' 
It ought not to be omitted, that Kepler also had given an 
impulse to Cavalieri in his '' New Method of Guaging," 
wliich is the earliest work with which we are acquainted, 
where principles of this sort are employed. 


Invention of the Telescope — Fracastoro — Porta — Refiect- 
ing Telescope — Roger Bacon — Digges — De Dominis — 
Jansen — Lipperhey — Galileo constructs Telescopes — Mi- 
croscopes — Re-elected Professor at Padua for life. 

The year 1609 was signalized by Galileo's discovery of 
the telescope, which, in the minds of many, is the princi- 
pal, if not the sole invention associated with his name. 


It cannot be denied that his fame, as the founder of the 
school of experimental philosophy, has been in an un- 
merited degree cast into the shade by the splendor of his 
astronomical discoveries ; yet Lagrange surely errs in the 
opposite extreme, when he almost denies that these form 
any real or solid part of the glory of this great man ; and 
Montucla omits an important ingredient in his merit, 
when he (in other respects very justly) remarks, that it 
required far less genius to point a telescope towards the 
heavens than to trace the unheeded, because daily recur- 
ring, phenomena of motion up to its simple and primary 
laws. We are to remember that in the days of Galileo, 
a telescope could scarcely be pointed to the heavens 
with impunity, and that a courageous mind was required 
to contradict, and a strong one to bear down a party, 
who, when invited to look on any object in the heavens 
which Aristotle had never suspected, immediately refu- 
sed all credit to those senses, to which, on other occa- 
sions, they so confidently appealed. It surely is a real 
and sohd part of Galileo's glory that he consumed his life 
in laborious and indefatigable observations, and that he 
persevered in announcing his discoveries undisgusted by 
the invectives, and undismayed by the persecutions to 
which they subjected him. Plagiarist ! Har ! impostor ! 
heretic ! w^ere among the expressions of malignant hatred 
lavished upon him, and although he also was not without 
some violent and foul-mouthed partisans, yet it must be 
told to his credit that he himself seldom condescended 
to notice these torrents of abuse, otherwise than by good- 
humored retorts, and by prosecuting his observations 
with renewed assiduity and zeal. 


The use of single lenses in aid of the sight had been 
long known. Spectacles were in common use at the be- 
ginning of the fourteenth century, and there are several 
hints, more or less obscure, in many early writers, of the 
effects which might be expected from a combination of 
glasses ; but it does not appear with certainty that any 
of diese authors had attempted to reduce their ideas to 
practice. After the discovery of the telescope, almost 
every country endeavored to find in the writings of its 
early philosophers traces of the knowledge of such an 
instrument, but in general with success very inadequate 
to the zeal of their national prepossessions. There are 
two authors especially to whom the attention of Kepler 
and others was turned immediately upon the promulga- 
tion of the discovery, as containing the germ of it in their 
works. These are Baptista Porta and Gerolamo Fra- 
castoro. We have already had occasion to quote the 
Homocentrica of Fracas tor o, who died in 1553 ; the fol- 
lowing expressions, though they seem to refer to actual 
experiment, yet fall short of the meaning with which it 
has been attempted to invest them. After explaining 
and commenting on some phenomena of refraction tlirough 
different media, to which he was led by the necessity of 
reconciling his theory with the vai^iable magnitudes of 
the planets, he goes on to say — ''For which reason^ 
those things which are seen at the bottom of w^ater ap- 
pear greater than those which are at the top ; and if any 
one looks through two eyeglasses, one placed upon the 
other ^ he will see every thing much larger and nearer." 
It should seem that this passage (as Delambre has al- 
ready remarked) rather refers to the close apphcation of 


one glass upon another ; and it may fairly be doubted 
whether any thing analogous to the composition of the 
telescope was in the writer's thoughts. Baptista Porta 
writes on the same subject more fully ; — '' Concave 
lenses show distant objects most clearly, convex those 

I which are nearer, whence they may be used to assist the 
sight. With a concave glass distant objects will be seen, 
small, but distinct ; with a convex one those near at 
hand, larger, but confused ; if you know rightly hoio to 
combine one of each sort^ you icill see both far and near 

I objects larger and clearer. '^'^ These words show, if Porta 
really was then unacquainted with the telescope, how 

^ close it is possible to pass by an invention without light- 

1 ing on it, for of precisely such a combination of a con- 
vex and concave lens, fitted to the ends of an organ pipe 
by way of tube, did the whole of Galileo's telescope 
consist. If Porta had stopped here, he might more se- 
curely have enjoyed the reputation of the invention, but 
he then professes to describe the construction of his in- 
strument, which has no relation whatever to his previous 
remarks. '' I shall now endeavor to show in what man- 
ner we may contrive to recognize our friends at the dis- 
tance of several miles, and how those of weak sight may 
read the most minute letters from a distance. It is an 
invention of great utility, and grounded on optical princi- 
ples, nor is it at all difBcult of execution ; but it must be 
so divulged as not to be understood by the vulgar, and 
yet be clear to the sharpsighted. " The description 
which follows seems far enough removed from the ap- 
prehended danger of being too clear ; and indeed every 
WTiter who has hitherto quoted it, has merely given the 



passage in its original Latin, apparently despairing of an 
intelligible translation. With some alterations in the 
punctuation, which appear necessary to bring it into any 
grammatical construction,* it may be supposed to bear 
something like the following meaning : — ^' Let a view be 
contrived in the centre of a mirror, where it is most ef- 
fective. All the solar rays are exceedingly dispersed, 
and do not in the least come together (in the true cen- 
tre ;) but there is a concoiu'se of all the rays in the cen- 
tral pai't of said mirror, half way towaixls the other cen- 
ti'e, vs'here the cross diameters meet. This view is con- 
trived in the following manner. A concave cylindrical 
mirror placed directly in front, but with its axis inclined, 
must be adapted to that focus : and let obtuse angled or 
right angled triangles be cut out with two cross lines on 
each side drawn from the centre, and a glass (specillum) 
will be completed fit for the pm^poses we mentioned." 
If it were not for the word speciUum^ wliich in the pass- 
age immediately preceding tliis, Porta f contrasts with 
speculum^ and which he afterwards explains to mean a 
glass lens, it would be very clear that the foregoing pass- 

* The passage in the original, which is printed Eilike in the editions of 
1598, 1607, 1619, and 1650, is as follows : — Visus constituatur centro valen- 
tissimus speculi, ubi fiet, et valentissime, universales solares radii dispergun- 
tur, et coeuRt minime, sed centro pi^gedicti speculi in illius medio, ubi dia- 
metri ti-ansversales, omnium ibi concursus. Constituitur hoc modo speculum 
concavum columnare aequidistantibus lateribus, sed lateri uno obliquo sec- 
tionibus illis accomodetur, trianguli vero obtusianguli, vel orthogonii secentnr, 
hinc inde duobus transversalibus lineis, excentro eductis. Et confectum erit 
specillum, ad id, quod diximus, utile. 

t Diximus de Ptolemeei speculoy sive specillo potius, quo per sexcentena 
millia pervenientes naves conspiciebat. 


age (supposing it to have any meaning) must be referred J 
to a reflecting telescope, and it is a little singular that i 
while this obscure passage has attracted universal atten- ^ 
tion, no one, so far as we are aware, has taken any no- \ 
tice of the following unequivocal description of the prin- i 
cipal part of Ne\^ton's construction of the same instru- i 
ment. It is in the 5th chapter of the 17th book, where i 
Porta explains by what device exceedingly minute let- \ 
ters may be read without difficulty. '^ Place a concave \ 
mirror so that the back of it may he against your 
breast ; opposite to it, and within the bimiing point, | 
place the writing ; put a plane mirror behind it, that may i 
be under your eyes. Then the images of the letters i 
which are in the concave mirror, and which the concave 
has magnified, will be reflected in the plane mirror, so 
that you may read without difficulty." 

We have not been able to meet with the Itahan trans- 
lation of Porta's Natural Magic, which was published in 
1611, under his own superintendence; but the English 
translator of 1658 would probably have known if any 
intelligible interpretation were there given of the mys- 
terious passage above quoted, and his translation is so 
devoid of meaning as strongly to militate against this , 
idea. Porta, indeed, claimed the invention as his own, 
and is believed to have hastened his death, (which hap- 
pened in 1615, he being then 80 years old,) by the 
fatigue of composing a Treatise on the Telescope, in 
which he had promised to exhaust the subject. We do 
not know whether this is the same work which was pub- 
Hshed after his death by Stelliola, but wliich contains no 
allusion to Porta's claim, and possibly SteUiola may have 


thought it most for his friend's reputation to suppress it. 
Schott says, a friend of his had seen Porta's book in 
manuscript and that it did at that time contain the as- 
sertion of Porta's title to the invention. After all, it is 
not improbable that he may have derived his notions of 
magnifying distant objects from our celebrated countryman 
Roger Bacon, who died about the year 1300. He has 
been supposed, not without good grounds, to have been 
one of the first who recognized the use of single lenses 
in producing distinct vision, and he has some expressions 
with respect to their combination which promise effects 
analogous to those held out by Porta. In '^ The Admir- 
able Force of Art and Nature," he says, '^ Physical figur- 
ations are far more strange, for in such manner may we 
frame perspects and lookingglasses that one thing shall 
appeare to be many, as one man shall seeme a whole 
armie ; and divers sunnes and moones, yea as many as 
we please, shall appeare at one time, &c. And so may 
the perspects be framed, that things most farre off may 
seeme most nigh unto us, and clean contrarie, soe that 
we may reade very small letters an incredible distance 
from us, and behold things how little soever they be, 
and make stars to appeare wheresoever we will, &c. 
And, besides all these, we may so frame perspects that 
any man entering into a house he shall indeed see gold, 
and silver, and precious stones, and what else he will, 
but when he maketh haste to the place he shall find just 
nothing." It seems plain, that the author is here speak 
ing solely of mirrors, and we must not too hastily draw 
the conclusion, because in the first and last of these as- 
sertions he is, to a certain extent, borne out by facts, 



that he therefore was in possession of a method of ac- 
complishing the middle problem also. In the previous j 
chapter, he gives a long list of notable things, (much in j 
the style of the Marquis of Worcester's Century of In- ' 
ventions) wliich, if we can really persuade ourselves that! 
he was capable of accomplishing, we must allow the! 
present age to be still immeasurably inferior to him in ' 
science. | 

Thomas Digges, in the preface to liis Pantometria, ? 
(pubUshed in 1591) declares, '' My father, by his continu- 1 
all painfull practises, assisted with demonstrations mathe- j 
maticall, was able, and sundry times hath by proportional! j 
glasses, duely situate in convenient angles, not only dis- ■ 
couered things farre off, read letters, numbered peeces ? 
of money, with the verye coyne and superscription there- ^ 
of, cast by some of his freends of purpose, upon downes 
in open fields ; but also, seuen miles off, declai*ed what ( 
hathe beene doone at that instant in priuate places. He^ 
hath also sundiie times, by the sunne beames, fii'ed pow- j 
der and discharde ordnance halfe a mile and more dis- 
tante ; which things I am the boulder to report, for that I 
there are yet livmg diverse (of these his dooings) occu- 
lati testes, (eye witnesses) and many other matters farre 
more strange and rare, which I omit as impertinent to 
this place." 

We find another pretender to the honor of the discov- 
ery of the telescope in the celebrated Antonio de Domi- 
nis. Archbishop of Spalatro, famous in the annals of op- 
tics for being one of the first to explain the theory of the 
rainbow. Montucla, following P. Boscovich, has scarce- 
ly done justice to De Dominis, whom he treats as a 


mere pretender and ignorant person. The indisposition 
of Boscovich towards him is sufficiently accounted for 
by the circumstance of his being a CathoHc prelate who 
had embraced the cause of Protestantism. His nominal 
reconciliation with the Church of Rome would probably 
not have saved him from the stake, had not a natural 
death released him when imprisoned on that account at 
Rome. Judgment was pronounced upon him notwith- 
standing, and his body and books were publicly burnt in 
the Campo de' Fiori, in 1624. His treatise, De Radiis. 
(which is very rarely to be met with,) was published by 
Bartolo after the acknowledged invention of the telescope 
by Gahleo ; but Bartolo tells us, in the preface, that the 
manuscript was communicated to him from a collection 
of papers wTitten twenty yeai's before, on his inquiring 
the Archbishop's opinion with respect to the newly dis- 
covered instrument, and that he got leave to publish it, 
'' with the addition of one or two chapters." The treat- 
ise cotitains a complete description of a telescope, which, 
however, is professed merely to be an improvement on 
spectacles, and if the author's intention had been to in- 
terpolate an after-^vritten account, in order to secure to 
himself the undeserved honor of the invention, it seems 
improbable that he vrould have suffered an acknowledg- 
ment of additions, previous to publication, to be inserted 
in the preface. Besides, the whole tone of the work is 
that of a candid and truth-seeking philosopher, very far 
indeed removed from being, as Montucla calls him, con- 
spicuous for ignorance even among the ignorant men of 
his age. He gives a drawing of a convex and concave 
lens, and traces the passage of the rays through them ; 


to which he subjoins, that he has not satisfied himself 
with any determination of the precise distance to which 
the glasses should be separated, accordmg to their con- 
vexity and concavity, but recommends the proper dis- 
tance to be found by actual experiment, and tells us, that 
the effect of the instrument will be to prevent the confu- 
sion arising from the interference of the direct and re- 
fracted rays, and to magnify the object by increasing the 
visible angle under which it is viewed. These, among 
the many claimants, are certainly the authors who ap- 
proached the most nearly to the discovery ; and the read- 
er may judge, from the passages cited, whether the 
knowledge of the telescope can with probability be re- 
ferred to a period earlier than the commencement of the 
17th century. At all events, we can find no earlier 
trace of its being applied to any practical use ; the 
knowledge, if it existed, remained speculative and barren. 
In 1609, Gahleo, then being on a visit to a friend at 
Venice heard a rumor of the recent invention, by a Dutch 
spectacle-maker, of an instrument which was said to rep- 
resent distant objects nearer than they usually appeared. 
According to his own account, this general rumor, which 
was confirmed to him by letters from Paris, w^as all that 
he learned on the subject ; and returning to Padua, he 
immediately applied himself to consider the means by 
which such an effect could be produced. Fuccarius, in 
an abusive letter which he wi'ote on the subject, asserts 
thaf one of the Dutch telescopes had been at that time ac- 
tually brought to Venice, and that he (Fuccarius) had seen 
it ; which, even if true, is perfectly consistent with Ga- 
lileo's ^ atement , and in fact, the question, whether or 


not Galileo saw the original instrument, becomes impor- 
tant only from his expressly asserting the contrary, and 
professing to give the train of reasoning by which he 
discovered its principle ; so that any insinuation that he 
had actually seen the Dutch glass, becomes a direct im- 
peachment of his veracity. It is certain, from the fol- 
lowing extract of a letter from Lorenzo Pignoria to Paolo 
Gaaldo that one at least of the Dutch glasses had been 
sent to Italy. It is dated, Padua, 31st August, 1609. 
'' We have no news, except the return of His Serene 
Highness, and the re-election of the lectiu'ers, among 
whom Sign. Galileo has contrived to get 1000 florins 
for Ufe ; and it is said to be on account of an eyeglass, 
like the one ichich was sent from Flanders to Cardinal 
Borghese, We have seen some here, and truly they 
succeed well." 

It is allowed by every one that the Dutchman, or rath- 
er Zealander, made his discovery by mere accident, 
which greatly derogates from any honor attached to it ; 
but even this diminished degree of credit has been fierce- 
ly disputed. According to one account, which appears 
consistent and probable, it had been made for sometime 
before its importance was in the slightest degree under- 
stood or appreciated, but was set up in the optician's 
shop as a curious pliilosphical toy, showing a large and 
inverted image of a weathercock, towards which it was 
directed. The Marquis Spinola, chancing to see it, was 
sti'uck with the phenomenon, purchased the instrument, 
and presented it either to the Archduke Albert of Austria, 
or to Prince Maurice of Nassua, whose name appears in 



every version of the story, and who first entertained the ! 
idea of employing it in military reconnoissances. 

Zacharias Jansen, and Henry Lipperhey, two specta^ 
cle-makers, living close to each other, near the church of ' 
Middleburg, have both had strenuous supporters of their ] 
title to the invention. A third pretender appeared after- ; 
wards in the person of James Metius of Alkmaer, who I 
is mentioned by Huyghens and Des Cartes, but his claims j 
rest upon no authority whatever comparable to that which 1 
supports the other two. About half a century afterwards, j 
Borelli was at the pains to collect and pubhsh a number ; 
of letters and depositions which he procured, as well on | 
one side as on the other. It seems that the truth lies : 
between them, and that one, probably Jansen, was the | 
inventor of the microscope^ which application of the prin- | 
ciple was unquestionably of an earher date, perhaps as 
far back as 1590. Jansen gave one of his microscopes j 
to the Archduke, who gave it to Cornelius Drebbel, a ^ 
salaried mathematician at the court of our James the | 
first, where William Borelli (not the author above men- 
tioned) saw it many years afterwards, when ambassador «i 
from the United Provinces to England, and got from | 
Drebbel this account of the quarter whence it came. \ 
Lipperhey afterwards in 1609, accidentally hit upon the i 
telescope^ and on the fame of this discovery it would not 
be difficult for Jansen, already in possession of an instru- : 
ment so much resembling it, to perceive the slight dif- i 
ference between them, and to construct a telescope in- i 
dependently of Lipperhey, so that each, with some show i 
of reason, might claim the priority of the invention, i 
A notion of this kind reconciles the testimony of many i 


conflicting witnesses on the subject ; some of whom do 
not seem to distinguish very accurately whether the tel- 
escope or microscope is the instrument to which their 
evidence refers. Borelli arrives at the conclusion, that 
Jansen was the inventor ; but not satisfied with this, he 
endeavors, with a glaring partiality which makes his for- 
mer determination suspicious, to secure for him and his 
son the more solid reputation of having anticipated Gali- 
leo in the useful employment of the invention. He has, 
however, inserted in his collections a letter from John the 
son of Zacharias, in which John, omitting all mention 
of his father, speaks of his own observation of the 
sateUites of Jupiter, evidently seeking to insinuate that 
they were earher than Galileo's ; and in this sense the 
letter has since been quoted, although it appears from 
John's own deposition, preserved in the same collection, 
that at the time of their discovery he could not have 
been more than six years old. An oversight of this sort 
throws doubt on the whole of the pretended observations, 
and indeed the letter has much the air of being the pro- 
duction of a person imperfectly informed on the subject 
on which he writes, and probably was compiled to suit 
Borelli 's purposes, which were to make Galileo's share in 
the invention appear as small as possible. 

Galileo himself gives a very intelligible account of the 
process of reasoning, by which he detected the secret. — 
'^ I argued in the following manner. The contrivance 
consists either of one glass or of more — one is not suffi- 
cient, since it must be either convex, concave, or plane ; 
the last does not produce any sensible alteration in ob- 
jects, the concave diminishes them : it is true that the 


convex magnifies, but it renders them confused and in- 
distinct ; consequently, one glass is insuiBcient to pro- 
duce the desired effect. Proceeding to consider two 
glasses, and bearing in mind that the plane glass causes no 
change, I determined that the instrument could not con- 
sist of the combination of a plane glass with either of the 
other two. I therefore applied myself to make expe- . 
riments on combinations of the two other kinds, and thus 
obtained that of which I was in search." It has been 
urged against Galileo, that if he really invented the tele- 
scope on tl^eoretical principles, the same theory ought 
at once to have conducted him to a more perfect instru- 
ment than that which he at first constructed ; but it is 
plain, from this statement, that he does not profess to 
have theorized beyond the determination of the species 
of glass which he should employ in his experiments, and 
the rest of his operations he avows to have been purely 
empirical. Besides, we must take into account the diffi- 
culty of grinding the glasses, particularly when fit tools 
were yet to be made ; and something must be attributed ' 
to Galileo's eagerness to bring his results to the test of 
actual experiment, without waiting for that improvement 
which a longer delay might and did suggest. Galileo's 
language bears a resemblance to the first passage which 
we quoted from Baptista Porta, sufficiently close to 
make it not improbable that he might be assisted in his 
inquiries by some recollection of it, and the same pass- 
age seems, in like manner, to have recurred to the mind 
of Kepler, as soon as he heard of the invention. Gali- 
leo's telescope consisted of a plano-convex and plano- 
concave lens, the latter nearest the eye, distant from 


each other by the difference of their focal lengths, being, 
in principle, exactly the same with the modern opera 
glass. He seems to have thought that the Dutch glass 
was the same, but this could not be the case, if the 
above quoted particular of the inverted weathercock^ 
which belongs to most traditions of the story, be correct ; 
because it is the peculiarity of this kind of telescope 
not to invert objects, and we should be thus furnished 
widi a demonstrative proof of the falsehood of Fucca- 
rius' insinuation : in that case the Dutch glass must 
have been similar to what was afterwards called the as- 
tronomical telescope, consisting of two convex^lasses 
distant from each other by the sum of their f^^lengths. 
Tliis supposition is not controverted by the fact, that this 
sort of telescope was never employed by astronomers till 
long afterwards ; for the fame of Galileo's observations, 
and the superior excellence of the instruments construct- 
ed under his superintendence, induced every one in the 
first instance to imitate his constructions as closely as 
possible. The astronomical telescope was,, however, 
eventually found to possess superior advantages over that 
which Gahleo imagined, and it is on this latter principle 
that all modern refracting telescopes are constructed ; 
the inversion being counteracted in those which are in- 
tended for terrestrial observations, by the introduction 
of a second pair of similar glasses, which restore the in- 
verted image to its original position. 

Galileo, about the same time constructed microscopes 
on the same principle, for we find that in 1612, he pre- 
sented one to Sigismund, king oif Poland ; but his at- 
tention being principally devoted to the employment 


and perfection of his telescope, the microscope remained : 
a long time imperfect in his hands : twelve years later, 
in 1624, he wrote to P. Federigo Cesi, that he had de- \ 
layed to send the microscope, the use of which he there ^ 
describes, because he had only just brought it to perfec- i 
tion, having experienced some difficulty in working the j 
glasses. Scbott tells us an amusing story, in his '' Magic \ 
of Nature,>^of a Bavarian philosopher, who, traveling in j 
the T)pQ'l with one of the newly invented microscopes i 
about mm, was taken ill on the road and died. The au- ' 
thorities of the village took possession of his baggage | 
and were proceeding to perform the last duties to his ' 
body, when, on examining the little glass instrmnent in 
his pocket, which chanced to contain a flea, they were ' 
struck with the greatest astonishment and terror, and the j 
poor Bavarian, condemned by acclamation as a sorcerer I 
who was in the habit of using a portable familiar, was; J 
declared unworthy of christian burial. Fortunately for 
his character, some bold sceptic ventured to open the 
instrument, and discovered the true nature of the impris- 
oned fiend. 

As soon as Galileo's first telescope was completed, he 
returned with it to Venice, and the extraordinary sensa- 
tion which it excited tends also strongly to refute Fuc- 
carius' assertion that the Dutch glass was already known 
there. During more than a month Galileo's whole time 
was employed in exhibiting his instrument to the princi- 
pal inhabitants of Venice, who thronged to his house to 
satisfy themselves of the truth of the wonderful stories in 
circulation; and at the end of that time the- Doge, Leon- 
ardo Donati, caused it to be intimated to him that such 


a present would not be deemed unacceptable by the sen- 
ate. Galileo took the hint, and his complaisance was 
rewarded by a mandate confirming him for life in his 
professorship at Padua, at the same time doubling his 
yearly salary, which was thus made to amount to 1000 

It was long before the phrenzy of public curiosity aba- 
ted. Sirturi describes a ludicrous violence which was 
done to himself, when, with the first telescope which he 
had succeeded in making, he went up into the tower of 
St. Mark at Venice, in the vain hope of being there en- 
tirely unmolested. Unluckily he was seen by some 
idlers in the street: a crowd soon collected round him, 
who insisted on taking possession of his instrument, and 
handing it one to the other, detained him there for sev- 
eral hours till their curiosity was satiated, when he was 
allowed to return home. Hearing them also inquire ea- 
gerly at what inn he lodged, he thought it better to quit 
Venice early the next morning, and prosecute his obser- 
vations in a less inquisitive neighborhood. Instruments 
of an inferior description w^ere soon manufactured, and 
vended every where as philosophical playthings, much 
in the way in which, in our own time, the kaleidoscope 
spread over Europe as fast as travelers could carry them. 
But the fabrication of a better sort was long confined, al- 
most solely, to Galileo and those whom he immediately 
instructed; and so late as the year 1637, we find Gaert- 
ner, or as he chose to call himself, Hortensius, assuring 
Galileo that none could be met with in Holland suffi- 
ciently good to show Jupiter's disc well defined ; and in 
1634 Gassendi begs for a telescope from Galileo, in- 


forming him that he was unable to procure a good one, 
either in Venice, Paris, or Amsterdam. 

The instrument, on its fii'st invention, was generally 
known by the names of Galileo's tube, the perspective, 
the double eye-glass : the names of telescope and micro- 
scope were suggested by Demisiano, as we are told by 
Lagalla in his treatise on the Moon. 


Discovery of Jupiter^ s Satelites — Kepler — Sizzi — Astrolo- 
gers — McBstlin — Horhy — Mayer, 

As soon as Galileo had provided himself with a second 
instrument, he began a careful examination of the heav- 
enly bodies, and a series of splendid discoveries soon re- 
warded his diligence. After considering the beautiful ap- 
pearances which the varied surface of the moon presented 
to this new instrument, he turned his telescope towards 
Jupiter, and his attention was soon arrested by the singu- 
lar position of three small stars, near the body of that 
planet, which appeared ahiiost in a straight line with it, 
tmd in the direction of the ecliptic. The following eve- 
ning he w^as surprised to find that two of the tlii'ee which 
had been to the eastwai'd of the planet, now appeared on 
the contrary side, which he could not reconcile with the 
apparent motion of Jupiter among the fixed stars, as given 



by the tables. Observing these night after night, he 
could not fail to remark that they changed their relative 
positions. A fourth also appeared, and in a short time 
he could no longer refuse to beheve that these small stars 
were four moons, revolving round Jupiter in the same 
manner in which our earth is accompanied by its single 
attendant. In honor of his patron, Cosmo, he named 
them the Medicaean stars. As they are now hardly kno\\-n 
by this appellation, his doubts, whether he should call 
them Medicaean, after Cosmo's family, or Cosmical, from 
his individual name, are become of less interest. 

An extract from a letter which Galileo received on 
this occasion from the court of France, will serve to 
show how highly the honor of giving a name to these new 
planets was at that time appreciated, and also how much 
was expected from Gahleo's first success in examining 
the heavens. '' The second request, but the most press- 
uig one which I can make to you, is, that you should 
determine, if you discover any other fine star, to call it 
by the name of the great star of France, as well as the 
most briUiant of all the earth ; and, if it seems fit to 
you, call it rather by his proper name of Henri, than by 
the family name of Bourbon : thus, you will have an 
opportunity of doing a thing just and due and proper in 
Itself, and at the same time will render yourself and your 
family rich and powerful for ever.'' The writer then 
proceeds to enumerate the different claims of Henri IV. 
to this honor, not forgetting that he married into the 
family of the Medici, &c. 

The result of these observations was given to the 
world, in an Essay which Galileo entitled .Ymcius 


SidereuSj or the Intelligencer of the Stars ; and it is 
difEciilt to describe the extraordinary sensation ^vhich its 
pubhcation produced. Many doubted, many positively 
refused to beheve, so novel an announcement ; all were 
struck with the greatest astonishment, according to their 
respective opinions, either at the new view of the uni- 
verse thus offered to them, or at the daring audacity of 
Gahleo in inventing such fables. We shall proceed to 
extract a few passages from contemporary ^^Titers rela- 
tive to this book, and the discoveries announced in it. 

Kepler deserves precedence, both from his own ce- 
lebrity, and from the lively and characteristic account 
which he gives of his first receiving the intelligence : — 
" I was sitting idle at home, thinking of you, most excel- 
lent Galileo, and your letters, when the news was brought 
me of the discovery of four planets by the help of the 
double eye-glass. Wachenfels stopped his carriage at m}' 
door to tell me, when such a fit of wonder seized me at 
a report which seemed so very absurd, and I was tlii'0\^'n 
into such agitation at seeing an old dispute between us 
decided in this way, that between his joy, my coloring, 
and the laughter of both, confounded as w^e were by such 
a novelty, we were hardly capable, he of speaking, or I 
of listening. My amazement was increased by the asser- 
tion of Wachenfels, that those who sent this news from 
Galileo were celebrated men, far removed by their learn- 
ing, weight, and character, above vulgar folly ; that the 
book was actually in press, and would be published 
immediately. On our sepai^ating, the authority of Ga- 
hleo liad the greatest influence on me, earned by the 
accuracy of his judgment, and excellence of his un- 


derstanding ; so I immediately fell to thinking how 
there could be any addition to the number of the planets 
without overturning my Mysterium Cosmographicum, 
published thirteen years ago, according to wliich EucHd's 
five regular solids do not allow more than six planets 
round the sun." 

This was one of the many wild notions of Kepler's 
fanciful brain, among which he was lucky enough at 
length to hit upon the real and principal laws of the 
planetary motions. His theory may be briefly given in 
his own words : '' The orbit of the earth is the measure 
of the rest. About it circumscribe a dod6<5ahedron. 
The sphere including this will be that of Mai's. x\bout 
Mars' orbit describe a tetrahedron : the sphere contain- 
ing this will be Jupiter's orbit. Round Jupiter's describe 
a cube : the sphere including tliis will be Saturn's. Within 
the earth's orbit inscribe an icosahedron : the sphere in- 
scribed in it will be Venus's orbit. In Venus inscribe 
an octahedron : the sphere inscribed in it will be Mer- 
cury's. You have now the reason of the number of the 
planets :" for as there are \m more than the five regular 
sohds here enumerated, Kepler conceived this to be a 
satisfactory reason why the^ e could be neither more nor 
less than six planets. His letter continues : — '' I am so 
far from disbelieving the existence of the four circum- 
joviai planets, that I long for a telescope to anticipate 
you, if possible, in discovering two round Mars, (as the 
proportion seems to me to require,) six or eight round 
Saturn, and perhaps one each round Mercury and Ve- 

The reader has here an opportiinity of verifying Gah- 


leo's observation, that Kepler's method of philosophi- 
zing differed widely from his own. The proper line is 
certainly difficult to hit between the mere theorist and 
the mere observer. It is not difficult at once to condemn 
the former, and yet the latter will deprive himself of an 
important, and often indispensable assistance, if he neg- 
lect from time to time to consohdate his obsenations, 
and thence to conjectm^e the course of futui'e observation 
most likely to reward his assiduity. This cannot be 
more forcibly expressed than in the words of Leonardo 
da Vinci: '' Theory is the general, experiments are the 
soldiers. The interpreter of the works of nature is ex- 
periment ; that is never wrong ; it is our judgment which 
is sometimes deceived, because we are expecting results 
which experiment refuses to give. We must consult ex- 
periment, and vary the circumstances, till we have de- 
duced general rules, for it alone can furnish us with them. 
But you will ask, what is the use of these general rules ? 
I answer, that they direct us in our inquiries into nature 
and the operations of art. They keep us from deceiv- 
ing ourselves and others, by promising ourselves results 
which we can never obtain.'' 

In the instance before us, it is well known that, adopt- 
ing some of the opinions of Bruno and Brutti,* Galileo, 
even before he had seen the satellites of Jupiter, had al- 
low"ed the possibility of the discovery of new planets ; 
and we can scarcely suppose that they had weakened his 
belief in the probability of further success, or discoura- 

* The author here called Brutti was an Englishman ; his re^l name perhaps 
was Bruce. 


ged him from examining the other heavenly bodies. Kep- 
ler, on the contrary, had taken the opposite side of the 
argument ; but no sooner was tlie fallacy of liis &st po- 
sition undeniably demonsti'ated, than, passing at once 
from one extreme to the otlier, he framed an unsupported 
theory to account for the number of satelhtes wliich were 
round Jupiter, and for those which he expected to meet 
with elsewhere. Kepler has been styled the legislator 
of the skies ; liis laws were promulgated ratlier too ai'bi- 
trarily, and they often failed, as all laws must do which 
are not dra\m from a cai'efid observation of the natm^e of 
those who ai'e to be governed by them. Astronomers 
have reason to be grateful for the theorems wliich he 
was the first to estabUsh ; but so fai' as regards the pro- 
gress of the science of mductive reasoning, it is perhaps 
to be regretted, that the seventeen yeai's which he wasted 
in random and uncomiected guesses should have been 
finally rewai'ded, by discoveries splendid enough to shed 
deceitful lustre upon the method by wliich he arrived at 

Gahleo himself clearly perceived the fallacious nature 
of these speculations on numbers and proportions, and 
has expressed his sentiments concerning them very une- 
quivocally. '' How great and coimnon an error appears 
to me the mistake of those who persist in making their 
knowledge and apprehension the measm-e of the appre- 
hension and knowledge of God ; as if that alone were 
perfect, which they understand to be so. But I, on the 
contrary, obseiTe that Nature has other scales of perfec- 
tion, which we cannot comprehend, and rather seem dis- 
posed to class among imperfections. For instance, 



among the relations of different numbers, those appear tO 
us most perfect which exist between numbers nearly re- 
lated to each other ; as the double, the triple, the pro- 
portion of three to two, &c. ; those appear less perfect 
which exist between numbers remote from, and prime to 
each other ; as 11 to 7, 17 to 13, 53 to 37, &c.; and 
most imperfect of all do those appear which exist be- 
tween incommensurable quantities, which by us are name- 
less and inexpHcable. Consequently, if the task had 
been given to a man, of establishing and ordering the 
rapid motions of the heavenly bodies, according to his 
notions of perfect proportions, I doubt not that he would 
have arranged them according to the former rational pro- 
portions ; but, on the contrary, God, with no regard to 
our imaginary symmetries, has ordered them in propor- 
tions not only incommensurable and irrational, but alto- 
gether inappreciable by our intellect. A man ignorant 
of geometry may perhaps lament, that the circumference 
of a circle does not happen to be exactly three times the 
diameter, or in some other assignable proportion to it, 
rather than such that we have not yet been able to ex- 
plain what the ratio between them is ; but one who has 
more understanding will know that if they were other 
than they are, thousands of admirable conclusions would 
have been lost, and that none of the other properties of 
the circle would have been true: the surface of the sphere 
would not be a quadruple of a great circle, nor the cylin- 
der be to the sphere as tliree to two : in short, no part 
of geometry would be true, and as it now^ is. If one of 
our most celebrated arcliitects had had to distribute this 
vast multitude of fixed stars through the great vault of 


heaven, I believe he would have disposed them with 
beautiful arrangements of squares, hexagons, and octa- 
gons ; he would have dispersed the larger ones among 
the middle sized and the less, so as to correspond exact- 
ly with each other ; and then he would think he had 
contrived admirable proportions : but God, on the con- 
traiy, has shaken them out from His hand as if by 
chance, and we, forsooth, must tliink that He has scatter- 
ed them up yonder without any regularity, symmetry and 

It is worth remarking that the dangerous ideas of ap- 
titude and congruence of numbers had taken such deep 
and general root, that long afterwards, when the reality 
of Jupiter's sateUites was incontestably estabhshed, and 
Huyghens had discovered a similar sateUite near Saturn, 
he w^as so rash as to declare his behef, (unwai^ned by the 
vast progress which astronomy had made in his own 
time,) that no more satellites would be discovered, since 
the one which he discovered neai' Saturn, with Jupiter's 
four, and om- moon, made up the number six, exactly 
equal to the number of the principal planets. Every 
reader knows that this notion, so unworthy the genius of 
Huyghens, has been since exploded by the discovery 
both of new planets, and new satellites. 

Francesco Sizzi, a Florentine astronomer, took the 
matter up in a somewhat different strain from Kepler. — 
'' There are seven windows given to animals in the dom- 
icile of the head, through which the air is admitted to the 
rest of the tabernacle of the body, to enhghten, to warm 
and nourish it, w^hich are the principal parts of the ^ty^^o- 
xdc^o?, (or little world); two nostrils, tw^o eyes, tw^o ears. 


and a mouth ; so in the heavens, as in a ^xK^oxoa-f/^ig^ (or I 
great world,) tliere ai'e two favorable stars, two iinpro- i 
pitious, two Imninaries, and Mercury alone undecided | 
and indifferent. From wliich and many other similar i 
phenomena of nature, such as the seven metals, &€, i 
which it were tedious to enumerate, we gather that the i 
number of planets is necessarily seven. Moreover, the i 
satellites are invisible to the naked eye, and therefore j 
can exercise no influence on the eai'tli, and therefore \ 
would be useless, and therefore do not exist. Besides, ( 
as well the Jews and other ancient nations, as modem I 
Europeans have adopted the division of the week into ; 
seven days, and have named them from the seven plan- i 
ets: now if we increase the number of the planets, this i 
whole system falls to the ground.'' To these remarks i 
Galileo calmly repUed, that whatever their force might 
be, as a reason for believing beforehand that no more i 
than seven planets would be discovered, they hardly i 
seemed of sufficient weight to destroy the new ones when ; 
actually seen. I 
Others again, took a more dogged line of opposition, , 
without venturing into the subtle analogies and ai'guments 
of the philosopher just cited. They contented them- 
selves, and satisfied others, with the simple assertion, 
that such things were not, and could not be, and the man- 
ner in which they maintained themselves in their incredu- | 
lity was sufficiently ludicrous. " Oh, my deai^ Kepler,*' i 
says Galileo, ^' how I wish that we could have one .j 
hearty laugh together. Here, at Padua, is the principal 
professor of philosophy, whom I have repeatedly and | 
urgently requested to look at the moon and planets through j 


my glass, which he pertinaciously refuses to do. Why 
are you not here? what shouts of laughter we should have 
at this glorious folly ! and to hear the professor of philos- 
ophy at Pisa laboring before the grand duke with logical 
arguments, as if with magical incantations, to charai the 
new^ planets out of the sk}^" Ca^ 

Another opponent of Galileo deserves to be named^ 
were it only for the singular impudence of the charge he 
ventures to bring against him. ^^ We are not to think, '^ 
says Cliristmann, in the Appendix to his Jsl)dm Gor- 
diuSj ^' that Jupiter has four satelhtes given him by na- 
tui'e, in order, by revolving round him, to immortalize 
tlie name of the Medici, who first had notice of the obser- 
vation. These are the dreams of idle men^ who love 
ludicrous ideas better than our laborious and industiious 
correction of the heavens. — Nature abhors so horri- 
ble a chaos, and to the truly wise, such vanity is detest- 

Galileo was also urged by the astrologers to attribute 
some influence, according to their fantastic notions, to the 
satellites, and the account which he gives his friend Dini 
of his answ^er to one of this class is well worth extracting, 
as a specimen of his method of uniting sarcasm with se- 
rious expostulation; ''I must," says he, ''tell you what 
I said a few days back to one of those nativity-casters, 
who beheve that God, when he created the heavens and 
the stars, had no tlioughts beyond what they can them- 
selves conceive, in order to free myself from his tedious 
importunity; for he protested, that unless I would declare 
to him the effect of the Medicsean planets, he would reject 
^and deny them as needless and superfluous. I beheve 


this set of men to be of Sizzi's opinion, that astronomers 
discovered the other seven planets, not by seeing them 
corporeally in the skies, but only from their effects oo 
earth, — much in the manner in which some houses are 
discovered to be haunted by evil spirits, not by seeing 
them, but from the extravagant pranks which are played i 
there. I replied, that he ought to reconsider the hundred ; 
or thousand opinions which, in the course of his life, he 
might have given, and particularly to examine well the 
events which he had predicted with the help of Jupiter, 
and if he should find that all had succeeded conformably 
to his predictions, I bid him prophecy merrily on, accor- 
ding to his old and wonted rules ; for I assured him that 
the new planets would not in any degree affect the things 
which are already past, and that in future he would not 
be a less fortunate conjuror than he had been : but if, on 
the contrary, he should find the events depending on Ju- 
piter, in some trifling particulars not to have agreed with 
his dogmas and prognosticating aph<^isms, he ought to 
set to w^ork to find new tables for calculating the constitu- 
tion of the four Jovial circulators at every bygone mo- 
ment, and, perhaps, from the diversity of their aspects, 
he woidd be able, with accurate observations and multi- 
plied conjunctions, to discover the alterations and varie- 
ty of influences depending upon them ; and I reminded 
him, that in ages past they had not acquired knowledge 
with httle labor, at the expense of others, from written 
books, but that the first inventors acquired the most ex- 
cellent knowledge of things natural and divine with study 
and contemplation of the vast book which nature holds 
ever open before those who have eyes in their forehead 


and in their brain ; and that it ^vas a more honorable and 
praiseworthy enterprise, with their own watching, toil, 
and study, to discover something admirable and new 
among the infinite number which yet remain concealed in 
the darkest depths of pilosophy) than to pass a listless and 
lazy existence, laboring only to darken the toilsome in- 
ventions of their neighbors, in order to excuse their o\mi 
cowardice mid inaptitude for reasoning, while they cry 
out that nothing can be -added to the discoveries already 

The extract given 'above from Kepler, is taken from 
an Essay, published with the later editions of the JS^un- 
cius^ the object and spirit of which seem to have been 
greatly misunderstood, even by some of Kepler's inti- 
mate friends. They considered it as a covert attack up- 
on Galileo, and, accordingly, Masstlin thus writes to him 
— ''In your Essay, (which I have just received,) you 
have plucked Galileo's feathers well ; I mean, that you 
have shown him not to be the inventor of the telescope^ 
not to have been the first to observe the irregularities of 
the moon's surface, not to have been the first discoverer 
of more worlds than the ancients were acquainted with^, 
&c. One som'ce of exultation was still left hmi, from 
the apprehension of which Martin Horky has now entire- 
ly delivered me." It is difficult to discover in what part 
of Kepler's\book Maestlin found all this, for it is one con- 
tinued enc^omium upon Galileo ; insomuch that Kepler 
almost apologises in the preface for what may seena his 
intemperate admiration of his friend. ^^ Some might 
wish I had spoken in more moderate terms in praise of 
Galileo, in consideration cf the distinguished men who 


are opposed to his opinions, but I have written nothing 
fulsome or insincere. I praise him, for myself; I leave 
other men's judgments free ; and shall be ready to join in 
condemnation, when some one wiser than myself, shall, 
by sound reasoning, point out his errors." However, 
Maestlin w^as not the only one w^ho misunderstood Kep- 
ler's intentions : the Martin Hoiky of whom he speaks, 
a young German, also signalized himself by a vain attack 
upon the book which he thought his patron Kepler con- 
demned. He was then traveling in Italy whence he 
WTOte to Kepler his first undetermined thoughts about the 
new discoveries. '' They are wonderful ; they are stu- 
pendous ; whether they are true or false I cannottell ."* 
He seems soon to have decided that most reputation was 
to be gained on the side of Galileo's opponents, and his 
letters accordingly became filled with the most rancorous 
abuse of him. At the same time, that the reader may 

* It may seem extraordinaiT that any one could support an argument by 
this partial disbelief in the instrument, which was allowed on all hands to 
represent terrestrial objects correctly. A similar instance of obstinacy, in 
an almost identical case, though in a more unpretending station, once came 
under the writer's own observation. A farmer in Cambridgeshire, who had 
acquired some conftised notions of the use of the quadrant, consulted him on 
a new method of determining the distances and magnitudes of the sun and 
moon, which he declared were far different from tbe quantities usually as- 
signed to them. After a little conversation, the root of his error, certainly 
sufficiently gross, appeared to be that he had confounded the angular measure 
of a degree, with 69 1-2 miles, the linear measure of a degree on the earth's 
surface. As a short w^ay of showing his mistake, he was desired to deter- 
mine, in the same manner, die height of his barn, which stood about 30 
yards distant ; he lifted the quadrant to his eye, but percieving probably, the 
monstrous size to w4iich his principles were forcing him, he said " Oh, sir, 
the quadi-ant 's only true for the sky." He must have been an objector of 
this kind who said to Gahleo, — " Oh, sir, the telescope 's only true for the 


appreciate Horky's own character, we shall quote a short 
sentence at the end of one of his letters, where he \mtes of 
a paltry piece of dishonesty with as great glee as if he 
had solved an ingenious and scientific problem. After 
mentioning his meetmg Gahleo at Bologna, and being 
indulged with a trial of his telescope, which, he says, 
'' does wonders upon the eai'di, represents celestial ob- 
jects falsely ;" he concludes with the follow^ing honorable 
sentence : — '' I must confide to you a theft which I com- 
mitted. I contrived to take a mould of the glass in wax, 
widiout the knowledge of any one, and, when I get 
home, I trust to make a telescope even better than Gali- 
leo's own.'' 

Horky having declai'ed to Kepler, '' I will never con- 
cede his four new planets to that Italian from Padua 
though I die for it," followed up this declaration by pub- 
Ushing a book against Galileo, which is the one alluded 
to by Masstlin, as having destroyed the little credit 
which, according to his view, Kepler's pubhcation had 
left him. This book professes to contain the examina- 
tion of four principal questions touching the alleged plan- 
ets ; 1st, Whether they exist ? 2nd, What they are ? 3rd, 
What they are Uke ? 4th, Why they are ? The first 
question is soon disposed of,' by Horky's declaring posi- 
tively that he has examined the heavens with Galileo's 
own glass, and that no such thing as a satelHte about 
Jupiter exists. To the second, he declares solemnly, 
that he does not more surely know that he has a soul in 
his body, than that reflected rays are the sole cause of 
Galileo's erroneous observations. In regard to the third 


question, he says, that these planets are like the small- 
est fly compared to an elephant ; and, finally, concludes 
on the fourth, that the only use of them is to gratify 
Galileo's "thirst of gold," and to afford himself a sub- 
ject of discussion. 

Galileo did not condescend to notice tins impertinent 
folly ; it was answered by Roffini, a pupil of Magini, 
and by a young Scotchman of the name of Wedderbum, 
then a student at Padua, and afterwards a physician at the 
Court of Vierma. In the latter reply we find it men- 
tioned, that Galileo was also using his telescope for the 
examination of insects, &c. Horky sent his perform- 
ance triumphantly to Kepler, and, as he returned home 
before receiving an answer, he presented himself before 
his patron in the same misapprehension under which he 
had written ; but the philosopher received him with a 
burst of indignation which rapidly undeceived him. The 
conclusion of the story is characteristic enough to be 
given in Kepler's own account of the matter to Gaileo, 
in which, after venting his wrath against this '' scum of a 
fellow," whose " obscurity had given him audacity," he 
says, that Horky begged so hard to be forgiven, that 
"I have taken him again irito favor upon this preliminary 
condition, to which he has agreed : — that I am to show 
him Jupiter's satellites, and he is to see them, and 
own that they are there." 

In the same letter Kepler writes, that although he has 
himself perfect confidence in the truth of Galileo's asser- 
tions, yet he wishes he could furnish him with some 
corroborative testimonies, which Kepler could quote in 
^guing the point with others. This request produced 


the following reply, from wliich the reader will also learn 
the new change which had now taken place in Galileo's 
fortunes, the result of the correspondence with Florence, 
part of which we have aheady extracted. '' In the first 
place, I return you my thanks that you first, and almost 
alone, before the question had been sifted (such is your 
candor and tire loftiness of your mind) , put faith in my 
assertions. You tell me you have some telescopes, but 
not sufficiently good to magnify distant objects with 
clearness, and that you anxiously expect a sight of mine, 
which magnifies images more than a thousand times. It 
is mine no longer, for the Grand Duke of Tuscany has 
asked it of me, and intends to lay it up in liis museum, 
among his most rare and precious curiosities, in eternal 
remembrance of the invention : I have made no other 
of equal excellence, for the mechanical labor is very 
great : I have, however, devised some instruments for 
figuring and polishmg them which I am unwilling to con- 
struct here, as they coLild not conveniently be carried to 
Florence, where I shall in future reside. You ask, my 
dear Kepler, for other testimonies: — I produce, for one, 
the Grand Duke, who, after observing the Medicaean 
planets several times with me at Pisa during the last 
months, made me a present, at parting, worth more than 
a tliousand florins, and has now invited me to attach my- 
self to him with the annual salaiy of one thousand flor- 
ins, and with the title of Philosopher and Principal 
Mathematician to His Highness; without the duties of 
any office to perform, but with the most complete lei- 
sure; so that I can complete my Treatises on Mechan- 
ics, on die Constitution of the Universe, and on Natural 


and Violent Local Motion, of which I have demonstra- 
ted geometrically many new and admirable phenomena. 
I produce, for another witness, myself, who, although 
already endowed in this college with the noble salar}^ of 
one thousand florins, such as no professor of mathemat- 
ics ever before received, and which I might securely en- 
joy during my life, even if these planets had deceived 
me and should disappear, yet quit this situation, and be- 
take me where want and disgrace will be my punish- 
ment should I prove to have been mistaken." 

It is difficult not to regret that Galileo should be thus 
called on to resign his best glasses ; but it appears prob- 
able that on becoming more familiar with the Grand 
Duke, he ventured to suggest that this telescope would 
be more advantageously employed in his own hands, 
than pompously laid up in a museum; for in 1637 we 
find him saying, in answer to a request from his friend 
Micanzio to send him a telescope — '' I am sorry that I 
cannot oblige you with the glasses for your friend, but I 
am no longer capable of making them, and I have just 
parted with two tolerably good ones which I had, re- 
serving only my old discoverer of celestial novelties 
which is already promised to the Grand Duke." Cosmo 
was dead in 1637, and it is his son Ferdinand who is 
here meant, who appears to have inherited his father's 
love of science. Galileo tells us, in the same letter, 
that Ferdinand had been amusing himself for some 
months with making object-glasses, and always carried 
one with him to work at wherever he went. 

When forwarding this telescope to Cosmo in the first 
instance, Galileo adds, with a very natural feeling — ''I 


send it to his higliness iinadorned aiid unpolished, as I 
made it for my own use, and beg that it may ahvays be 
left in the same state; for none of the old parts ought to 
be displaced to make room for new ones, which will 
have had no shai^e in the watchings and fatigues of these 
observations." A telescope was in existence, though 
with the object glass broken, at the end of the last cen- 
tury, and probably still is in the museum at Florence, 
which was showTi as the discoverer of Jupiter's satel- 
lites. NeUi, on whose authority tliis is mentioned, ap- 
pears to question its genuineness. The first reflecting 
telescope, made with Nemon's own hands, and scarcely 
possessing less interest than the first of Galileo's, is pre- 
served in the library of the Royal Society. 

By degrees the enemies of Galileo and of the new 
stars found it impossible to persevere m their disbelief, 
whether real or pretended, and at length seemed resolved 
to compensate for the sluggishness of their perception, 
by its acuteness when brough into action. Simon May- 
er pubhshed his '' Mundus Joviahs " in 1614, in which 
he claims to have been an original observer of the satel- 
lites, but, with an affectation of candor, allows that Gali- 
leo observed them probably about the same time. The 
eai'hest observation which he has recorded is dated 29th 
December, 1609, but, not to mention the total want of 
probability that Mayer would not have immediately pub- 
lished so interesting a discovery, it is to be observed, 
that, as he used the old style, this date of 29th Decem- 
ber agrees with the 8th January, 1610, of the new 
style, which was the date of Galileo's second observation, 

I 2 


and Galileo ventured to declare his opinion, that this 
pretended observation was in fact a plagiarism. 

Scheiner counted five, Rheita nine, and other observ- 
ers, with increasing contempt for Galileo's imperfect an- 
nouncements, carried the number as high as twelve. 
In imitation of Galileo's nomenclature, and to honor the 
sovereigns of the respective observers, these supposed 
additional satellites were dignified with the names of 
Vladislavian, Agrippine, Urbanoctavian, and Ferdinand- 
otertian planets ; but a very short time served to show it 
was as unsafe to exceed as to fall short of the number 
wliich Galileo had fixed upon, for Jupiter rapidly remov- 
ed himself from the neighborhood of the fixed stars, 
which gave rise to these pretended discoveries, carrying 
with him only his four original attendants, which continu- Ji 
ed in every part of his orbit to revolve regidarly about 'i 

Perhaps we cannot better wind up diis accoiuit of the i| 
discovery of Jupiter's satelHtes, and of the mtense inter- I 
est they have at all times inspired, than in the words of ^ 
one who inherits a name worthy to be ranked witli that of j 
Galileo in the hst of astronomical dicoverers, and who , 
takes Ms o^^-n place among the most accomphshed math- i 
ematicians of the present times, ^'The discovery of 
these bodies was one of tlie first brilliant results of the 1 
invention of tlie telescope; one of the first great facts 
which opened the eyes of mankind to the system of the i 
universe, which taught them the comparative insignifi- i 
cance of their own planet, and the superior vastness and ; 
nicer mechanism of those other bodies, which had be- ; 
fore been distinguished from the stai's only by their mo- ; 


tion, and wherein none but the boldest thinkers had 
ventured to suspect a community of nature with our own 
globe. This discovery gave the holding turn to the 
opinions of mankind respecting the Copernican system; 
the analogy presented by these httle bodies (litde how- 
ever only in comparison with the great central body 
about which they revolve) performing their beautiful rev- 
oludons in perfect harmony and order about it, being too 
strong to be resisted. This elegant system was vv'atched 
widi all the cmiosity and interest the subject naturally in- 
spired. The eclipses of the satellites speedily attracted 
attention, and the more when it was discerned, as it 
speedily was, by Galileo himself, that they afforded a 
ready method of determining the dijfference of longitudes 
of distant places on the earth's surface, by observations 
of the instants of their disappearances and reappearan- 
ces, simultaneously made. Thus the first astronomical 
solution of the great problem of tlie longitude^ the first 
mighty step which pointed out a connection between 
speculative astronomy and practical utihty, and which, re- 
placing the fast dissipating dreams of astrology by nobler 
visions, showed how the stars might really, and without 
fiction, be called arbiters of the destinies of empires, we 
owe to the satellites of Jupiter, those atoms impercepti- 
ble to the naked eye, and floating like motes in the 
beam of their primary — itself an atom to our s^ht, no- 
ticed only by the careless vulgar as a large star, and by 
the philosophers of former ages as something moving 
among the stars, they know not what^ nor why: perhaps 
only to perplex the wise with fruidess conjectures, and 
harass the weak with fears as idle as their theories."* 

— ■ jL 'ii 

♦ Herscbel'g Address to the Astronomical Society. 1827. 



Observations on the Moon — NebulcB — Saturn — Venus — 

There were other discoveries announced in Galileo's 
book of great and unprecedented importance, and which 
scarcely excited less discussion than the controverted 
MediccTan planets. His observations on the moon threw 
additional light on the constitution of the solar system, 
and cleared up the difficulties which encumbered the ex- 
planation of the varied appearance of her surface. The 
different theories current at that day, to account for these 
phenomena, are collected and described by Benedetti, 
and also with some Uveliness, in a mythological poem, 
by Marini. We are told, that, in the opinion of some, 
the dark shades on the moon's surface arise from the 
interposition of opaque bodies floating between her and 
the sun, \diich prevents his light from reaching those 
parts : others thought, that on account or her vicinity to 
the earth, she was partly tainted with the imperfection of 
our terrestrial and elementary nature, and was not of that 
entirely pure and refined substance of which the more 
remote heavens consist : a third party looked on her as 
a vast mirror, and maintained that the dark pains of her 
surface were the reflected images of oiu* earthly forests 
and mountains. 

Galileo's glass taught him to believe that the surface 
of tliis planet, far from being smooth and polishedj as 


was generally taken for granted, really resembled our 
earth in its structure ; he was able distinctly to trace on 
it the outlines of mountains and other inequalities, the 
summits of which reflected the rays of the sun before 
these reached the lower parts, and the sides of which, 
turned from his beams, lay bmied in deep shadow. He 
recognized a distribution into something similar to con- 
tinents of land, and oceans of water, which reflect the 
sun's light to us with greater or less vivacity, according 
to their constitution. These conclusions were utterly 
odious to the Aristotelians ; they had formed a pre- 
conceived notion of what the moon ought to be, and they 
lo'^ed the doctrines of Galileo, who took dehght, as 
they said, in distorting and ruining the fairest w^orks of 
nature. It was in vain he argued, as to the imaginary 
perfection of the spherical form, that although the moon^. 
or the earth, w^ere it absolutely smooth, would indeed 
be a more perfect sphere than in its present rough state^ 
yet toucliing the perfection of the earth, considered as a 
natural body calculated for a particular purpose, every 
one must see that absolute smoothness and sphericity^ 
would make it not only less perfect, but as far from be- 
ing perfect as possible. '^ What else, " he demanded, 
" would it be but a vast unblessed desert, void of ani- 
mals, of plants, of cities and of men ; the abode of si- 
lence and inaction ; senseless, lifeless, soulless, and stript 
of all those ornaments w^hich make it now so various and 
so beautiful ?" 

He reasoned to no purpose with the slaves of the an- 
cient schools : nothing could console them for the des- 
truction of their smooth, unalterable surface, and to such 


an absurd length was this hallucination carried, that one 
opponent of Galileo, Lodovico delle Colombe, constrain- 
ed to allow the evidence of the sensible inequalities of 
the moon's surface, attempted to reconcile the old doc- 
trine with the new observations, by asserting, that every 
part of the moon, which to the terrestrial observer ap- 
peared hollow and sunken, was in fact entirely and exact- 
ly filled up with a clear crystal substance, perfectly im- 
perceptible by the senses, but which restored to the moon 
her accurately spherical and smooth surface. Gahleo 
met the ai^gument in the mariner most fitting, according- 
to one of Aristotle's own maxims, that ^'it is foohsh to 
refute absurd opinions with too much curiosity." '' Tru- 
ly, " says he, " the idea is admirable, its only fault is, 
that it is neither demonstrated nor demonstrable ; but I 
am perfectly ready to beheve it, provided that, with 
equal courtesy, I may be allowed to raise upon your 
smooth surface, crystal mountains (which nobody can 
perceive) ten tiraes higher than those which I have actually 
seen and measured." By threatening to proceed to such 
extremities, he seems to have scared the opposite party- 
into moderation, for we do not find that the crystalline 
theory was persevered in. 

In the same essay, Galileo also explained at some 
length the cause of that part of the moon being visible, 
which is unenlightened directly by the sun in her first 
and last quarter. Masstlin, and before him Leonardo da 
Vinci, had already declared this to arise from what mayi 
be called eurthshine^ or the reflection of the sun's light 
from the terrestrial globe, exactly similai' to that which 
the moon affords us when we are similarly placed be- 1 


tween her and the sun ; but the notion had not been fa- 
vorably received, because one of the arguments against 
the eardi being a planet, revolving like the rest round 
the sun, was, that it did not shine hke them, and was 
therefore of a different nature ; and this argument, weak 
as it was in itself, the theory of terrestrial reflection 
completely overturned. The more popular opinions as- 
cribed this feeble light, some to the fixed stars, some to 
Venus, some to the rays of the sun, penetrating and shin- 
ing through the moon. Even the sagacious Benedetti 
adopted the notion of this light being caused by Venus, 
in the same sentence in which he explains the true reason 
of the faint Hght observed during a total eclipse of the 
moon, pointing out that it is occasioned by those rays of 
the sun, which reach the moon, after being bent round 
the sides of the earth by the action of our atmosphere. 

Galileo also announced the detection of innumerable 
stars, invisible to the unassisted sight ; and those remark- 
able appearances In the heavens, generally called nebulse, 
tlie most considerable of which is famihar to all under 
the name of the milky-way, when examined by his in- 
strument, were found to resolve themselves into a vast 
collection of minute stars, too closely congregated to 
produce a separate impression upon the unassisted eye.* 
Benedetti, who divined that the dark shades on tbe 
moon's surface arose from the constitution of those parts 

* This opinion, with respect to the milky-way, iiad beeli held by some of 
die ancient astronomers. See Manilus. Lib. i. v. 753. 

" Anne magis densa stelldrum turha corona 
Contexit flammds, et crasso lumine candety 
I JStfulgore nitet collato clarior orbisJ^ 


which suffered much of the light to pass into them, and 
consequently reflected a less portion of it, had maintained 
that tlie milky-way was the result of the converse of the , 
same phenomenon, and declared, in the language of his 
astronomy, that it was a part of the eighth orb, w^hich 
did not, like the rest, allow the sun's light to traverse , 
it freely, but reflected a small pait feebly to our sight. 

The .\nti-Copernicans would probably have been well ' 
pleased, if by these eternally renewed discussions and 
disputes, they could have occupied Galileo's time suffi- 
ciently to detain his attention from his telescope and as- 
tronomical observations ; but he knew^ too well w^here j 
his real strength lay, and they had scarcely time to com- 
pound any thing hke an argument against him and his 
theories, before they found him in possession of some 
new facts, which they w^ere unprepai^ed to meet, other- 
wise than by the never-failing resource of abuse and af- 
fected contempt. The year had not expired before Gali- 
leo had new intelligence to communicate, of the highest 
importance. Perhaps he had been taught caution by the 
numerous piracies which had been committed upon his 
discoveries, and he first announced his new discoveries 
enigmatically, veiling their real import by transpositions 
of the letters in the words w'hich described them, (a 
practice then common, and not disused even at a much 
later date,) and inviting all astronomers to declare, with- 
in a certain time, if they had noted any thing new in the 
heavens worthy of observation. The transposed letters 
which he published w^ere — 

*« Smaismrmilme poeia leumi hvne nu^taoirm* 

Kepler, in the true spirit of his riddling philosophy, en- 


deavored to decypher the meaning, and fancied he had 
succeeded when he formed a barbai'ous latin verse, 

" Salve umbistineum geminatum Martia proles.^' 

conceiving that the discovery, whatever it might be, re- 
lated to the planet Mars, to which Kepler's attention had 
before been particularly directed. The reader, howev- 
er, need not wearj" himself in seeking a translation of this 
solution, for, at the request of the Emperor Rodolph, 
Galileo speedily sent to him the real reading — 
' Altissimum planetam tergeminum ohservam ; 

that is, '' I have obser^'ed that the most distant planet is 
triple," or, as he further explains the matter, '^I have, 
with great admiration, observed that Saturn is not a sin- 
gle star, but three together, wirich, as it were, touch 
each other ; they have no relative motion, and are con- 
stituted in this form, oOo, the middle being somewhat 
larger than the lateral ones. If we examine them with 
an eye-glass which magnifies the surface less than 1000 
times, the three stars do not appear very distinctly, but 
Satui'n has an oblong appearance, like the appearance of 
an olive, thus, O- Now I have discovered a court for 
Jupiter, and two servants for this old man, who aid his 
steps and never quit his side." Galileo was, however, 
no match in this style of writing for Kepler, w^ho disap- 
proved his friend's metaphor, and, in liis usual fanciful 
and amusing strain — "I will not," said he, ''make an 
old man of Saturn, nor slaves of his attendant globes, but 
rather let this tricd^orate form be Geiyon, so shall Gali- 
leo be Hercules, and the telescope his club ; armed with 


which, he has conquered that distant planet, and dragged 
him from the remotest depths of nature, and exposed 
him to the view of all." Galileo's glass was not of suffi- 
cient power to show him the real constitution of this ex- 
traordinary planet ; it was reserved for Huyghens, about 
the year 1656, to declare to the world that these sup- 
posed attendant stars are, in fact, part of a ring which 
surrounds, and yet is completely distinct from the body 
of Saturn ; * and the still more accurate observations of 
Herschel have ascertained that it consists of two concen- 
tric rings revolving round the planet, and separated from 
each other by a space which oiu* most powerful teles- 
copes scarcely enable us to measure. 

Galileo's second statement concluded with the remark, 
that '' in the other planets nothing new was to be observ- 
ed ; " but a month had scarcely elapsed, before he com- 
municated to the world another enigma, 

H(2C immatura a mejamfrustra leguntur oy, 

which, as he said, contained the announcement of a new 
phenomenon, in the highest degree important to the truth 
of the Copemican system. The interpretation of this is, 

CynthicB figuras cemulatur mater amorum, 

that is to say, — Venus rivals the appearances of the moon 
— for Venus being now arrived at that part of her orbit 
in which she is placed between the eaith and the sun, 

♦Huygbens announced his discovery in this form : aaaaaaaccccc 
deeeeeghiiiiiiillllm m nnnnnnnnnooooppqrr 
stttttuuuuu, which he afterwai'ds recomposed into the sentence, An- 
nulo cingitur, tenui, piano, nusqaam cohcBrenie, ad eclipticam inclinato, 

e Saturni Luna. Hagge, 1656. 


and consequently, with only a pai't of her enhghtened 
surface turned towards the earth, the telescope shewed 
her in a crescent form, like the moon in a similar posi- 
tion, and tracing her through the whole of her orbit round 
the sun, or at least so long as she was not invisible from 
his overpowering hght, Galileo had the satisfaction of 
seeing the enhghtened portion in each position assume 
the form appropriate to that hypothesis. It was with 
reason, therefore, that he laid stress on the importance 
of this observation, which also estabhshed another doc- 
trine scarcely less obnoxious to the Anti-Copernicans, 
namely, that a new point of resemblance was here found 
between the earth and one of the principal planets ; and as 
the reflection from the earth upon the moon had shewn it 
to be luminous like the planets when subjected to the rays 
of the sun, so this change of appai^ent figure demonstra- 
ted tliat one of the planets, not near the eailh, and there- 
fore probably all, were in their o\mi nature not lumi- 
nous, and only reflected the sun's hght which fell upon 
them ; an inference, of which the probabilitj' was still 
faither increased a few years later by the observation 
of the transit of Mercujy over the sun's disc. 

It is cmious that only twenty-five years before this 
discovery of the phases (or appearances) of Venus, a 
commentator of Ai'istotle, under the name of LuciUus 
Philalth£eus,had advanced the doctrine that all the planets 
except the moon are luminous of themselves, and in 
proof of his assertion had mged, ''' that if the other plan- 
ets and fixed stars received their light from the sun, they 
would, as they approached and receded from him, or as 
he approached and receded from them, assume the same 


phases as the moon, ^vhich, he adds, we have never 
yet observed." — He further remarks, "• that Mercury 
and Venus would, in the supposed case of their being 
nearer the earth than the smi, eclipse it occasionally, 
just as eclipses are occasioned by the moon." Perhaps 
it is still more remarkable, that these veiy passages, in 
which the reasoning is so correct, though the facts are 
too hastily taken for granted, (the common error of that 
school,) are quoted by Benedetti, expressly to show the 
ignorance and presumption of the author. Copernicus, 
whose want of instruments had prevented him from ob- 
serving the horned appeai^ance of Venus when between 
the earth and sun, had perceived how formidable an ob- 
stacle the non-appeai'ance of this phenomenon presented 
to his system; he endeavored, though unsatisfactorily, 
to account for it by supposing that the rays of the sun 
passed freely tlirough the body of the planet, and Gali- 
leo takes occasion to praise him for not being deterred 
from adopting the system, which, on the whole, appeared 
to agree best with the phenomena, by meeting with some 
which it did not enable him to explain. Milton, whose 
poem is filled with allusions to Galileo and his astrono- 
my, has not suffered this beautiful phenomenon to pass 
unnoticed. After describing the creation of the Sun, he 
adds :— 

^ Hither, as to their fountain, other stars 
Repairing, in their golden urnS draw light. 
And hence the morning planet^ilds heV^rns. 

Galileo also assured himself, at the same time, that 
the fixed stars did not receive their fight from the sun. 
This he ascertained by comparing the vividness of their 


light, in all positions, with the feebleness of that of the 
distant planets, and by observing the different degrees of 
brightness with which all the planets shown at different 
distances from the sun. The more remote planets did 
not, of course, afford equal facihties with Venus for so 
decisive an observation; but Galileo thought he observ- 
ed, that when Mars was in quadratures, (or in the quar- 
ters, the middle points of his path on either side,) his 
figure varied slightly from a perfect circle. Gahleo 
concludes the letter, in which he announces these last 
observations to his pupil Castelli, with the following ex- 
pressions, showing how jusdy he estimated the opposi- 
tion they encountered:— '^ You almost make me laugh 
by saying that these clear observations are sufficient to 
convince the most obstinate: it seems you have yet to 
learn that long ago the observations were enough to con- 
vince those w^ho are capable of reasoning, and those who 
wish to learn the truth; but that to convince the obsti- 
nate, and those who care for nothing beyond the vain 
applause of the stupid and senseless vulgar, not even the 
testimony of the stars would suffice, were they to descend 
on earth to speak for themselves. Let us then endeavor 
to procure some knowledge for ourselves, and rest con- 
tented with this sole satisfaction; but of advancing in 
popular opinion, or gaining the assent of the book-phi- 
losophers, let us abandon both the hope and the desire." 




Account of the Academia Lincea — Del Cunento — Royal 

Galileo's resignation of the mathematical professorship 
at Padua occasioned much dissatisfaction to all those who 
were connected with that university. Perhaps not fully 
appreciating his desire of returning to his native country, 
aiid the importance to him, and to the scientific world in 
general, of the complete leisure which Cosmo secured 
to him at Florence, (for by the terms of his diploma he 
was not even required to reside at Pisa, nor to give any 
lectures, except on extraordinary occasions, to sovereign 
princes and other strangers of distinction,) the Venetians 
remembered only that they had offered him an honorable 
asylum when ahnost driven from Pisa ; that they had in- 
creased his salary to four times the sum which any pre- 
vious professor had enjoyed ; and, finally, by an almost 
unprecedented decree, that they had but just secured him 
in his post during the remainder of his life. Many took 
such offence as to refuse to have any further communica- 
tion with him; and Sagredo, a constant friend of Galileo, 
wrote him word that he had been threatened with a simi- 
lar desertion unless he should concur in the same pe- 
remptory resolution, which threats, however Sagredo, at 
the same time, intimates his intention of braving. 

Early in the year 1611, Galileo made his first appear- 
ance in Rome, where he was received with marks of 
distinguished consideration, and where all ranks were 



eager to share the pleasure of contemplating the new dis- 
coveries. '^ Whether we consider cardinal, prince, or 
prelate, he found an honorable reception from them all, 
and had their palaces as open and free to liim as the 
houses of his private friends." Among other distinc- 
tions he was sohcited to become a member of the newly- 
formed philosophical society, the once celebrated Acade- 
mia Lincea^ to which he readily assented. The founder 
of tliis society was Federigo Cesi, the Marchese di 
MonticeUi, a young Roman nobleman, the devotion of 
whose time and fortune to the interests of science has 
not been by any means rewarded with a reputation com- 
mensurate with his deserts. If the energy of his mind 
had been less wortliily employed than in fostering the 
cause of science and truth, anH in extending the advan- 
tages of his birth and fortune to as many as were willing 
to co-operate with him, the name of Federigo Cesi 
might have appeared more prominently on the page of 
history. Cesi had scarcely completed his 18th year, 
when, in 1603, he formed the plan of a philosophical 
society, which in the first instance consisted only of 
hunself and three of his most intimate friends, Hecke, a 
Flemish physician, Stelluti, and Anastasio de Filiis. 
Ce^'s father, the Duca d^ Acquasparta, who was of an 
arbitrary and extravagant temper, considered such pur- 
suits and associates as derogatory to his son's rank; he 
endeavored to thwart the design by the most violent and 
unjustifiable proceedings, in consequence of which, Cesi 
in the beginnmg of 1605 privately quitted Rome, Hecke 
was obliged to leave Italy altogether from fear of the 
Inquisition, which was excited against him, and the acad- 


emy was for a time virtually dissolved. The details off 
these transactions are foreign to the present narrative : it ' 
will be enough to mention that, in 1609, Cesi, who had > 
never altogether abandoned his scheme, found the oppo- I 
sition decaying which he at first experienced, and with I 
better success he renewed the plan which he had sketch- I 
ed six years before. A few extracts from the Regula- ' 
tions will serve to show the spirit in which this distin- 
guished society w^as conceived : — 

'' The Lyncean Society desires for its academicians, 
philosophers eager for real knowledge, who will give 
themselves to the study of nature, and especially to 
mathematics; at the same time it will not neglect the 
ornaments of elegant literature and philology, which hke a 
graceful garment adorn the whole body of science. — In 
the pious love of wisdom, and to the praise of the most 
good and most high God, let the Lynceans give their 
minds, first to observation and reflection, and afterwards 
to writing and publishing. — It is not within the Lyncean 
plan to find leisure for recitations and declamatory as- 
semblies; the meetings will neither be frequent nor full, 
and chiefly for transacting the necessary buisness of the 
society: but those who wish to enjoy such exercises Tvdll 
in no respect be hindered, provided they attend them as 
accessory studies, decently and quietly, and without mak- 
ing promises and professions of how much they are 
about to do. For there is ample philosophical employ- 
ment for every one by himself, particularly if pains are 
taken in traveling and in the observation of natural phe- 
nomena, and in the book of nature which every one has 
at home, that is to say, the heavens and the earth; and 


enough may be learaed from the habits of constant cor- 
respondence with each other, and akernate offices of 
counsel and assistance. — Let the first fruits of wisdom be 
love ; and so let the L}'nceans love each other as if uni- 
ted by the strictest ties, nor suffer any interruption of this 
sincere bond of love and faith, emanating from the source 
of virtue and philosophy. — Let them add to their names 
the title of Lyncean, which has been advisedly chosen 
as a warning and constant stimulus, especially when they 
write on any literaiy subject, also in their private letters 
to their associates, and in general vdien any work comes 
from them wisely and well performed. — The Lynceans 
will pass over in silence all political controversies and 
quarrels of every kind, and v/ordy disputes, especially 
gratuitous ones, which give occasion to deceit, unfriend- 
liness, and hatred ; like men who desire peace, and seek 
to preserve their studies free from molestation, and to 
avoid every sort of disturbance. And if any one by 
command of his superiors, or from some other necessity, 
is reduced to handle such matters, since they are foreign 
to physical and mathematical science, and consequently 
alien to the object of the Academy, let them be printed 
without the Lyncean name." ^ 

The society which was eventually organized formed 
but a very trifling part of the comprehensive scheme 
which Cesi originally proposed to himself ; it had been 

* Perhaps it was to deprecate the hostility of the Jesuits that, at the cbse 
of these Regulations, the Lynceans are directed to address their prayers, 
among other Saints, especially to Ignatius Loyola, as to one who greatly 
favored the interests of learning. Odescalchi. Memorie dell' Acad, de* 
Lincei, Roma. 1806. 


his wish to establish a scientific Order which should have 
corresponding lodges in the principal towns of Europe, 
and in other parts of the globe, each consisting of not 
more than five nor less than three members, besides an 
unlimited number of academicians not restricted to any 
particular residence or regulations. The mortifications 
and difficulties to which he was subjected from his fa- 
ther's unprincipled behaviour, render it most extraordina- 
ry and admirable that he should have ventured to under- 
take even so much as he actually carried into execution. 
He promised to furnish to the members of his society 
such assistance as they might require in the prosecution 
of their respective researches, and also to defray the 
charges of publishing such of their works as should be 
thought worthy of appearing with the common sanction. 
Such liberal offers were not hkely to meet with an unfa- 
vorable reception : they were thankfully accepted by 
many well qualified to carry his design into execution, 
and Cesi was soon enabled formally to open his academy , 
the distinctive title of which he borrowed from the Lynx 
with reference to the piercing sight which that animal 
has been supposed to possess. This quahty seemed to 
him an appropriate emblem of those which he desired to 
find in his academicians, for the purpose of investigating 
the- secrets of nature; and although, at the present day^ 
the name may appear to border on the grotesque, it was 
conceived in the spirit of the age, and the fantastic names 
of the numberless societies which were rapidly formed 
in various parts of Italy far exceed Avhatever degree of 
quaintness may be thought to belong to the Lyncean name. 
The Inflamed— the Transformed — the Uneasy — the Hu- 


morists — the Fantastic — the Intricate — the Inax)lent — 
the Senseless — the Undeceived — the jEtherial — tne Val- 
iant Societies are selected from a vast number of similar 
institutions, the names of which, now almost their sole 
remains, are collected by the industry of Morhof and 
Tiraboschi.* The Humorists are named by Morhof as 
the only Italian philosophical society anterior to the 
Lynceans ; their founder was Paolo Mancino, and the 
distinctive symbol which they adopted was rain dropping 
from a cloud, with the motto Redit agmine dulci ; — their 
title is derived from the same metaphor. The object of 
their union appears to have been similar to that of the 

, Lynceans, but they at no time attained to the celebrity 
to which Cesi's society rose from the moment of its in- 
corporation. Cesi took the presidency for his life, and 
the celebrated Baptista Porta was appointed vice presi- 
dent at Naples. Stelluti acted as the legal representative 
of the society, with the title of procuratore. Of the 
other two original members x\nastasio de Filiis was dead, 
and although Hecke returned to Italy in 1614, and re- 

I joined the Academy, yet he was soon afterwards struck 
off the list in consequence of his lapsing into insanity. 
Among the academicians we find the names of Galileo, 
Pabio Colonna, Lucas Valerio, Guiducci, Welser, Gio- 
vanni Pabro, Terrentio, Virginio Cesarini, Ciampoli, 
Molitor, Cardinal Barberino, (nephew of Pope Urban 
VIII.) SteUiola, Salviati, &c. 

* Polyhistor Literarius, &c. — Storia della Letterat. Ital. The still exis- 
ling society of Chaff, more generally known by its Italian title, Della Crusca, 
belongs to the same period. 


The principal monument still remaining of the zeal and j 
industry to which Cesi incited his academicians is the j 
Phytobasanos, a compendium of the natural historj^ of i 
Mexico, which must be considered a suprising perform- I 
ance for the times in which it appeared. It was written [ 
by a Spaniard named Hernandez; and Reecho, who i 
often has the credit of the whole work, made great ad- j 
ditions to it. Durmg fifty years the manuscript had been I 
neglected, when Cesi discovered it, and employed Ter- i 
rentio, Fabro, and Colonna, all Lynceans, to publish it ! 
enriched \vith their notes and emendations. Cesi him- i 
self pubhshed several treatises, two of which are extant ; ^ 
his Tabulm Phytosophicce^ and a Dissertation on Bees, j 
entitled Apiarium^ the only known copy of which last is | 
in the library of the Vatican. His great work, Theatrum i 
JVa^itrcB, was never printed ; a circumstance which tends ( 
to show, that he did not assemble the society round him 
for the purpose of ministering to his own vanit}^, but 
postponed the publication of his own productions to the 
labors of his coadjutors. Tliis, and many other valuable 
works belonging to the Academy, existed in manuscript, 
till lately in the Albani Library at Rome. Cesi collect- ■; 
ed, not a large, but an useful librarj^ for the use of the 
Academy, (which was afterwards augmented, on the pre- 
mature death of Cesarini, by the donation of his books ;) 
he filled a botanical garden with the rarer specimens of ; 
plants, and arranged a museum of natural curiosities ; his i 
palace at Rome was constantly open to the academi- ] 
cians ; his purse and his influence were employed with | 
equal liberality in their service. j 


Cesi's death, in 1632, put a sudden stop to the pros- 
perity of the society, a consequence which may be at* 
tributed to the munificence with which he had from the 
first sustained it : no one could be found to fill his place 
in the princely manner to which the academicians were 
accustomed, and the society, after lingering some years, 
under the nominal patronage of Urban VIII., gradually 
decayed, till, by the death of its principal members, and 
dispersion of the rest, it became entirely extinct. Bian- 
chi, whose sketch of the Academy was almost the only 
one till the appearance of Odescalchi's history, made an 
attempt to revive it in the succeeding century, but with- 
out any permanent effect. A society under the same 
name has been formed since 1784, and is still flourishing 
in Rome. Before leaving the subject it may be men- 
tioned, that one of the earhest notices that Bacon's 
works were known in Italy is to be found in a letter to 
Cesi, dated 1625 ; in which Pozzo, who had gone to 
Paris with Cardinal Barberino, mentions having seen 
them there with great admiration, and suggests that Ba- 
con would be a fit person to be proposed as a member 
of their society. After Galileo's death, three of his prin- 
cipal followers, Viviani, Torricelli, and Aggiunti formed 
the plan of establishing a similar philosopliical society, 
and though Aggiunti and Torricelli died before the 
scheme could be realized, Viviani pressed it forward, 
and, under the auspices of Ferdinand II., formed a socie- 
ty, which, in 1657, merged in the famous Academia del 
Cimento^ or Experimental Academy. This latter held 
its occasional meetings at the palace of Ferdinand's broth- 



er, Leopold de Medici ; it was composed chiefly, if not | 
entirely, of Galileo's pupils and friends. During the few I 
years that this society lasted, one of the principal objects 
of which was declared to be the repetition and develop- ! 
ment of Galileo's experiments, it kept up a correspond- 
ence with the principal philosophers in every part of ! 
Europe, but when Leopold was, in 1666, created a 
cardinal, it appears to have been dissolved, scarcely ten 
years after its institution. This digression may be ex- 
cused in favor of so interesting an establishment as the 
Academia Lincea which preceded by half a century the 
formation of the Royal Society of London, and Acad- i 
mie Francoise of Paris. ; 

These latter two are mentioned together, probably for j 
the first time, by Salusbury. The passage is curious in | 
an historical point of view, and worth extracting : — '' In I 
imitation of these societies, Paris and London have erec- j 
ted theu-s of Le$ Beaux Esprits^ and of the Virtuosi ; the | 
one by the countenance of the most eminent Cardinal | 
RicheHeu, the other by the royal encouragement of his ] 
sacred Majest}- that now is. The Beaux Esprits have \ 
pubhshed sundry volumes of their moral and physiologi- | 
cal conferences, with the laws and history of their fellow- ' 
ship ; and I hope the like in due time from our Royal \ 
Society ; that so, such as envie their fame and felicity, I 
and such as suspect their ability and candor, may be si- 
lenced and disappointed in their detractions and expect- 1 
ations." I 



Spots on the Sun— Essay on Floating Bodies — Sclieiner 
— Change in Saturn, 

Galileo did not indulge the cmiosity of his Roman 
friends by exliibiting only the wonders already mention- 
ed, wliich now began to lose the gloss of novelty, but 
disclosed a new discovery, which appeared still more 
extraordinary, and to the opposite faction, more hateful 
than any tiling of t\ hich he had yet spoken. This was the 
discovery, which he first made in the month of March, 
1611, of dark spots on the body of the sun. A curious 
fact, and one which well serves to illustrate Galileo's 
superiority in seeing things simply as they are, is, that 
these spots had been observed and recorded centuries 
before he existed, but, for want of careful observation, 
their true nature had been constantly misapprehended. 
One of the most celebrated occasions was in the year 
807 of our era, in which a dark spot is mentioned as 
visible on the face of the sun during seven or eight days. 
It was then supposed to be Mercury. Kepler, whose 
astronomical knowledge would not suffer him to over- 
look that it w^as impossible that Mercury could remain so 
long in conjunction with the sun, preferred to solve the 
difficulty by supposing that, in Aimoin's original account, 
the expression was not octo dies., (eight days) , but octoties 
— a barbarous word, wliich he supposed to have been 
written for octies^ (eight times); and that the other 
accounts (in which the number of days mentioned is 


different) copying loosely from the first, had both mis- 
taken the word, and misquoted the time Avhich they 
thought they found mentioned there. It is impossible 
to look on this explanation as satisfactory, but Kepler, 
who at that time did not dream of spots on the sun, was 
perfectly contented with it. In 1609, he himself ob- 
served upon the sun a black spot, which he in like man- 
ner mistook for Mercury, and unluckily the day be ng 
cloudy, did not allow him to contemplate it sufficiently 
long to discover his error, which the slowness of its ap- 
parent motion would soon have pointed out. He has- 
tened to publish his supposed observation, but no sooner 
v/as Galileo's discovery of the solar spots amiounced, 
than he, with that candor which as much as his flightly 
disposition certainly characterized him at all times, re- 
tracted his former opinion, and owned his belief that he 
had been mistaken. In fact it is known from the more 
accurate theory which we now possess of Mercury's 
motions, that it did not pass over the sun's face at the 
time when Kepler thought he perceived it there. 

Gahleo's observations were in their consequences to 
him particularly unfortunate, as in the course of the con- 
troversy in which they engaged him, he first became 
personally embroiled with the powerful party, w^hose 
prevailing influence was one of the chief causes of his 
subsequent misfortunes* Before we enter upon that dis- 
cussion, it will be proper to mention another famous 
treatise which Galileo produced soon after his return 
from Rome to Florence, in 1612. This is his Dis- 
course on Floating Bodies, which restored Arcliimedes' 
theory of hydrostatics, and has, of course, met with the 


opposition which few of Galileo's works failed to en- 
counter. In the coniniencement, he thought it necessa- 
ry to apologize for writing on a subject so different from 
that which chiefly occupied the pubhc attention, and de- 
clared that he had been too closely occupied in calcula- 
ting the periods of the revolutions of Jupiter's satellites 
to permit him to pubhsh anything earher. These peri- 
ods he had succeeded in determining during the pre- 
ceding year, wliilst at Rome, and he now announced 
them to complete their circuits, the first in about 1 day, 
181-2 hours; the second in 3 days, 13 hours, 20 
minutes; the third in 7 days, 4 houi^s; and the outermost 
in 16 days, 18 hours. All these numbers he gave 
merely as approximately true, and promised to continue 
his observations, for the purpose of correcting the re- 
sults. He then adds an amiouncement of his recent 
discovery of the solar spots, ''which, as they change 
their situation, offer a strong argument, either that the 
sun revolves on itself, or that, perhaps, other stars, 
like Venus and Mercury, revolve about it, invisible at 
all other times, on account of the small distance to 
which they are removed from him." To tlrls he after- 
wards subjoined, that, by continued observation, he had 
satisfied himself that these solar spots were in actual 
contact witli the surface of the sun, where they are 
continually appearing and disappeaiing; that their figured 
were very irregular, some being very dark, and others 
not so black ; that one would often divide mto three or 
four, and, at other times, two, three, or more would 
unite into one ; besides wliich, that they had all a com- 



men and regular motion, with which they revoh^e round 
with the sun, which turned upon its axis in about tlie 
time of a lunar month. 

Having by these pr^atory observations as^yaged the 
public thirst for astronomteal novelties, he ventures to 
introduce the principal subject of the treatise above 
mentioned. The question of floating bridges had been 
discussed at one of the scientific parties, assembled at 
the house of Galileo's friend, Salviati, and the general 
opinion of the company appearing to be that the floating 
or sinking of a body depended principally upon its 
shape, Galileo undertook to convince them of their 
error. If he had not preferred more direct arguments, 
he might merely have told them that in this instance 
they were opposed to their favorite Aristotle, whose 
words are very unequivocal on the point in dispute. 
'^ Form is not the cause why a body moves downwards 
rather than upwards, but it does affect the swiftness 
with which it moves; " which is exactly the distinction 
which those who called themselves Aristotelians were 
unable to perceive, and to w^hich the opinions of Aris- 
totle himself were not always true. Galileo states the 
discussion to have immediately arisen from the assertion 
of some one in the company, that condensation is the 
effect of cold, and ice was mentioned as an instance- 
On this, Galileo observed, that ice is rather water rare- 
fied than condensed, the proof of which is, that ice 
always floats upon water. It was replied, that the 
reason of this phenomenon was, not the superior light- 
ness of the ice, but its incapacity, owing to its flat 


shape, to penetrate and overcome the resistance of the 
water. Galileo denied this, and asserted that ice of any 
shape would float upon water, and that, if a flat piece of 
ice were forcibly taken to the bottom, it would of itself 
rise again to the surface. Upon this assertion it appears 
that the conversation became so clamorous, that Galileo 
thought it pertinent to commence his Essay with the 
following observation on the advantage of delivering sci- 
entific opinions in waiting, '^because in conversational 
arguments, either one or other party, or perhaps both, 
are apt to get overwarm, and to speak overloud, and 
either do not suffer each other to be heard, or else, 
transported with the obstinacy of not yielding, wander 
far away from the original proposition, and confound 
both themselves and their auditors with the novelty and 
variety of their assertions." After this gentle rebuke 
he proceeds with his argument, in which he takes occa- 
sion to state the famous hydrostatical paradox, of which 
the earliest notice is to be found in Stevin's works, a 
contemporary Flemish engineer, and refers it to a prin- 
ciple on which we shall enlarge in another chapter. He 
then explains the true theory of buoyancy, and refutes 
the false reasoning on which the contrary opinions were 
founded, with a variety of experiments. 

The whole value and nterest of experimental process- 
es generally depends on a variety of minute circumstan- 
ces, the detail of which would be particularly unsuited 
to a sketch like the present one. For thc^e who are 
desirous of becoming more familiar with Galileo's mode 
of conducting an argument, it is fortunate that such m 


series of experiments exists as that contained in this 
essay ; experiments which, from their simphcity, admit 
of being for the most part concisely enumerated, and at 
the same time possess so much intrinsic beauty and 
characteristic power of forcing conviction. They also 
present an admirable specimicn of the talent for which 
Galileo was so deservedly famous, of inventing ingenious 
arguments in favor of his adversaries' absurd opinions 
before he condescended to crush them, showing that 
nothing but his love of truth stood in the way of his be- 
ing a more subtle sophist than any amongst them. In 
addition to these reasons for giving these experiments 
somewhat in detail, is the fact tliat all explanation of one 
of the principal phenomena to which they allude is omit- 
ted in many more modern treatises on Hydrostatics; 
and in some it is referred precisely to the false doctrines 
here confuted. 

The marrow of the dispute is included in Galileo's 
assertion, that '' The diversity of figiu'e given to any sol- 
id cannot be in any way the cause of its absolutely sink- 
ing or floating : so that if a solid, when formed, for exam- 
ple, into a spherical figure, sinks or floats in the water, the 
same body will sink or float in the same water, when put 
into any other form. The breadth of the figure may 
indeed retard its velocity, as well of ascent as descent, and 
more and more accordmg as the said figure is reduced to 
a greater breadth and thinness ; but that it may be reduced 
to such a form as absolutely to put an end to its motion 
in the same fluid, I hold to be impossible. In this I 
have met with great contradictors who, producing some 


experiments, and in particular a thin board of ebony, 
and a ball of the same wood, and showing that the ball in 
water sinks to the bottom,* and that the board if put hghtly 
on the surface floats, have held and confirmed themselves 
in their opinion with the authority of Aristotle, that the 
cause of that rest is the breadth of the figure, unable by 
its small weight to pierce and penetrate the resistance of 
the water's thickness, which is readily overcome by the 
other spherical figure." — For the purpose of thesQ ex- 
periments, Galileo recommends a substance such as wax, 
which may be easily moulded into any shape, and with 
which, by the addition of a few filings of lead, a substance 
may be readily made of any required specific gravit}^ 
He then declares that if a ball of wax of the size of an 
orange, or bigger, be made in this manner heavy enough 
to sink to the bottom, but so lightly that if we take from 
it only one grain of lead it returns to the top ; and the 
same wax be afterwards moulded into a broad and thin 
cake, or into any other figure, regular or irregular, the 
addition of the same grain of lead will always make it 
sink, and it will again rise when we remove the lead from 
it. '^ But methinks I hear some of the adversaries 
raise a doubt upon my produced experiment : and, first, 
they offer to my consideration that the figure, as a figure 
simply, and disjunct from the matter, works no efiect, 
but requires to be conjoined with the matter ; and, 
moreover, not with every matter, but with those only 
wherewith it may be able to execute the desired opera- 
tion. Just as w^e see by experience that an acute and 
sharp angle is more apt to cut than an obtuse ; yet 

♦ Ebony is one of the few woods heavier than water. 


always provided that both one and the other are joined 
with a matter fit to cut, as for instance, steel. There- 
fore a knife with a fine and sharp edge cuts bread or 
wood with much ease, which it will not do if tlie edge be 
blunt and thick ; but if, instead of steel, any one will 
take wax and mould it into a knife, undoubtedly he will 
never learn the effects of sharp and blunt edges, because 
neither of them will cut ; the wax being unable, by rea- 
son of its flexibility, to overcome the hardness of the 
w^ood and bread. And therefore, applying the like dis- 
course to our argument, they say that the difference of 
figure will shew different effects with regard to floating 
and sinking, but not conjoined with any kind of matter, 
but only with those matters which by their weight are 
able to overcome the viscosity of the w^ater, (Hke the 
ebony w^hich they have selected) ; and he that will select 
cork or other light wood to form solids of different fig- 
ures, would in vain seek to find out what operation fig- 
ure has ill sinking or floating because all w^ould sw4m, 
and that not through any property of this or that figure^ but 
through the debility of the matter." 

'' When I begin to examine one by one all tlse par- 
ticulars here produced, I allows not only that figures, 
simply as such, do not operate in natural things, but also 
that they are never separated from the corporeal sub- 
stance, nor have I ever alleged them to be stript of sen- 
sible matter : and also I freely admit, that hi our en- 
deavors to examine the diversity of accidents which de- 
pend upon the variety of figures, it is necessary to apply 
tliem to matters which obstruct not the various operations 
of those various figures. 1 admit and grant that I should 


do very ill if I were to try the influence of a sharp edge 
with a knife of wax, applying it to cut an oak, because 
no sharpness in wax is able to cut that very hard wood. 
But yet, such an experiment of this knife would not be 
beside the purpose to cut curded milk, or other very 
yieldmg matter ; nay, in such matters, the wax is more 
convenient than steel for finding the difference depend- 
ing on the acuteness of the angles, because milk is cut in- 
differently with a razor, or a blunt knife. We must 
therefore have regard not only to the hai'dness, solidity, 
or weight of the bodies which under different figures, are 
to divide some matters asunder ; but also, on the other 
hand, to the resistance of the matter to be penetrated. 
And, since-I have chosen a matter which does penetrate 
the resistance of the water, and in all figures descends to 
the bottom, my antagonists can charge me with no de- 
fect ; nor (to revert to their illustration) have I attempted 
to test the efficacy of acuteness by cutting with matters 
unable to cut. I subjoin withal, that all caution, dis- 
tinction, and election of matter would be superfluous and 
unnecessary, if the body to be cut should not at all resist 
the cutting : if the knife were to be used in cutting a 
j inist or smoke, one of paper would serve the purpose as 
' well as one of Damascus steel ; and I assert that this is 
^ tlie case with water, and that there is not any solid of 
such hghtness or of such a figure, that being put on the 
water it will not divide and penetrate its thickness ; and 
if you will examine more carefully your thin boards of 
wood, you will see that they have part of their thickness 
under water ; and, moreover, you wiU see that the shavings 
of ebony, stone, or metal, when they float, have not on- 


\y thus broken the continuity of the water, but are with 
all their thickness under the surface of it ; and tliat 
more and more, according as the jfloating substance is 
heavier, so that a thin floating plate of lead will be lower 
than the surface of the surrounding water by at least 
twelve times the thickness of the plate, and gold will 
dive below the level of the water almost twenty times 
the thickness of the plate, as I shall show presently." 

In order to illustrate more clearly the non-resistance 
of water to penetration, Galileo then directs a cone to 
be made of wood or wax, and asserts that when it floats, 
either with its base or point in the water, the solid con- 
tent of the part immersed will be the same, although the 
point is, by its shape, better adapted to overcome the 
resistance of the water to division, if that were the cause of 
the buoyancy. Or the experiment may be varied by tem- 
pering the wax with filings of lead, till it sinks in tlie water, 
when it will be found that in any figure the same cork 
must be added to it to raise it to the surface. — -'This 
silences not my antagonists ; but they say that all the dis- 
course hitherto made by me imports little to them, and that 
it serves their turn, that they have demonstrated in one 
instance, and in such manner and figure as pleases them 
best, namely, in a board and a ball of ebony, that one, 
when put into the water, sinks to the bottom, and that the 
other stays to swim at the top ; and the matter being the 
same, and the two bodies differing in nothing but in fig- 
ure, they affirm that with all perspicuity they have dem- 
onstrated and sensibly manifested what they undertook. 
Nevertheless, I believe, and tliink I can prove, that this 
very experiment proves nothing against my theory. And 


first, it is false that the ball sinks, and the board not ; for 
the board will sink too, if you do to both the figures as 
the words of our question require ; that is, if you put 
them both in the water ; for to be in the water imphes 
to be placed in the water ; and, by Aristode's own defi- 
nition of place, to be placed imports to be environed by 
tiie sui'face of the ambient body ; but when my antago- 
nists show the floating board of ebony, they put it not in- 
to the water, but upon the water ; where, Being detained 
by a certain impediment (of which more anon) it is sur- 
rounded, partly with water, partly with air, wnich is con- 
trary to our agreement ; for that was, that the bodies 
should be in the water, and not part in the water, part in 
the air. I will not omit another reason, founded also up- 
on experience, and, if I deceive not myself, conclusive 
against the notion that figure, and the resistance of water 
to penetration, have anything to do with the buoyancy of 
bodies. Choose a piece of wood, or other matter, as for 
instance, wahiut-wood, of which a ball rises from the 
bottom of the water to the surface more slowly than a 
ball of ebony of the same size sinks, so that clearly the 
ball of ebony divides the water more readily in sinking 
than does the walnut in rising. Then take a board of 
walnut-tree equal to and like the floating ebony one of 
my antagonists ; and if it be true that this latter floats by 
reason of the figure being unable to penetrate the water, 
the other of walnut-tree, without all question, if thrust to 
the bottom ought to stay there, as having the same im- 
peding figure, and being less apt to overcome the said 
resistance of the water. But if we find, by experience, 




that not only the thin board, but every other figure of the 
same walnut-tree will return to float, as unquestionably 
we shall, then I must desire my opponents to forbear to 
attribute the floating of the ebony to the figure of the 
board, since the resistance of the water is the same in 
rising as in sinking, and the force of ascension of the 
walnut-tree is less than the ebony's force for going to the 

'' Now, let us return to the thin plate of gold or silver, 
or the thin board of ebony, and let us lay it lightly upon 
the water, so that it may stay there without smking, and 
carefully observe the eflect. It will appear clearly, that 
the plates are a considerable matter lower than the sur- 
face of the water wliich rises up, and makes a kind of 
rampart round them on every side, in the manner shown 
in the annexed figure, in which B D L F represents the 

surface of the water, and A E I the surface of the 
plate. But if it have already penetrated and overcome 
the continuity of the water, and is of its own natui'e 
heavier than the water, why does it not continue to sink, 
but stop and suspend itself in that little dimple that its 
weight has made in the water ? My answer is, because 
in sinking till its surface is below the water which rises 
up in a bank round it, it draws after and carries along 
with it the air above it, so that that which in this case 


descends and is placed in the water, is not only the 
board of ebony or plate of iron, but a compound of ebo- 
ny and air, from which composition results a soUd no 
longer specifically heavier than the water, as was the eb- 
ony or gold alone. But, Gentlemen, we want the same 
matter ; you are to alter nothing but the shape ; and 
therefore have the goodness to remove this air, which 
may be done simply by washing the upper surface of the 
board, for the water having once got between the board 
and air will run together, and the ebony will go to the 
bottom ; and if it does not, you have won die day. But 
methinks I heai^ some of my antagonists cunningly oppo- 
sing tliis, and telhng me that they will not on any account 
allow their board to be wetted, because the weight of the 
water so added, by making it heavier than it was before, 
draws it to the bottom, and that the addition of new 
weight is contrary to our agreement, which was, that the 
matter should be the same." 

'^ To this I answer first, that nobody can suppose 
bodies to be put into the water v/ithout their being wet, 
nor do I wish to do more to the board than you may do 
to the ball.- Moreover, it is not true that the board sinks 
on account of the weight of the water added in the wash- 
ing ; for I will put ten or twenty drops on the floating 
boai^d, and so long as they stand separate it shall not 
sink ; but if the board be taken out, and all that water 
wiped off, and the whole surface bathed with one single 
drop, and put it again upon the water, there is no ques- 
tion but it will sink, the other water running to cover it, 
being no longer hindered by the air. In the next place, 
it is altogether false that water can in any way increase 


the weight of bodies immersed in it, for water has no 
weight in water, since it does not sink. Now, just as he 
who should say, that brass by its own nature sinks, but 
that when formed into the shape of a kettle, it acquires 
from that figure a virtue of lying in the water without sink- 
ing, would say what is false, because that is not purely 
brass which then is put into the water, but a compound 
of brass and air ; so is it neither more nor less false, that 
a thin plate of brass or ebony swims by virtue of its dila- 
ted and broad figure. Also I cannot omit to tell my op- 
ponents, that this conceit of refusing to bathe the surface 
of the board, might beget an opinion in the third person 
of a poverty of arguments on their side, especially as the 
conversation began about flakes of ice, in which it would 
be simple to require that the surfaces should be kept 
dry ; not to mention that such pieces of ice, whether 
wet or dry, always float, and as nay antagonists say, be- 
cause of their shape." 

'' Some may wonder that I affirm this power to be in 
the air of keeping the plate of brass or silver above wa- 
ter, as if in a certain sense I would attribute to the air a 
kind of magnetic virtue for sustaining heavy bodies with 
which it is in contact. To satisfy all these doubts, I have 
contrived the following experiment to demonstrate how 
truly the air does support these sohds ; for I have founds 
when one of these bodies which floats when placed light- 
ly on the water, is thoroughly bathed and sunk to the 
bottom, that by carrying down to it a Uttle air without 
otherwise touching it in Ihe least, I am able to raise and 
carry it back to the top, w^here it floats as before. To 
this effect, I take a ball of wax;> and with a little lead 


make it just heavy enough to sink very slowly to the bot- 
tom, taking care that its sui'face be quite smooth and 
even. This, if put gently into the water, submerges al- 
most entirely, there remahiing visible only a httle of the 
very top, which, so long as it is joined to the air, keeps 
the ball afloat ; but if we take away the contact of the 
air, by wetting this top, the ball sinks to the bottom, and 
remains there. Now to make it return to the surface by 
virtue of the air wliich before sustained it, thrust into the 
water a glass, with the mouth do^^Tiwards, which will 
carry with it tlie air it contains ; and move this down 
towards the ball, until you see by the transparency of the 
glass that the air has reached the top of it ; then gently 
draw the glass upwai^ds, and you will see the ball rise, 
and afterwards stay on the top of the water, if you care- 
fully part the glass and water without too much disturb- 
ing it.* There is therefore a certain affinity between the 
air and other bodies, which holds them united, so that 
they separate not without a kind of violence, just as be- 
tween water and other bodies ; for in drawing them 
wholly out of the water, we see the water follow them, 
and rise sensibly above the level before it quits them." 
Having established this principle by tliis exceedingly in- 
genious and convincing experiment, Galileo proceeds to 
show from it what must be the dimensions of a plate of 
any substance which will float as the wax does, assuming 
in each case that we know the greatest height at which 

* In making this very l)eautiful experiment, it is best to keep the glass a 
few seconds in the water, to give time for the surface of the ball to drv'. It 
will also succeed with a light needle, if carefully conducted. 
M 2 


the rampart of water will stand round it. In like manner 
he shows that a pyramidal or conical figure may be made 
of any substance, such that by the help of air, it shall 
rest upon the water without whetting more than its base ; 
and that we may so form a cone of any substance that it 
shall float if placed gently on the surface, with its point 
downwards, w^hereas no care or pains will enable it to 
float with its base downwards, owing to the different 
proportions of air which in the two positions remain 
connected with it. With this parting blow at his antag- 
onist's theory we close our extracts from this admirable 

The first elements of the theory of running waters 
were reserved for Castelli, an intimate friend and pupil 
of Galileo. On the present occasion, Castelli appeared 
as the ostensible author of a defense against the attacks 
made by Vincenzio di Grazia and by Lodovico delle Co- 
lumbe (the author of the crystaline composition of the 
moon) on the obnoxious theory. After destroying all 
the objections which they produced, the writer taunting- 
ly bids them remember, that he was merely Galileo's 
pupil, and consider how much more effectually Galileo 
himself would have confuted them, had he thought it 
worth v/hile. It w^as not known till several years after 
his death, that this Essay was in fact written by Galileo 

These compositions merely occupied the leisure time 
which he could withhold from the controversy on the 
solar spots to which we have aheady alluded. A Ger- 
man Jesuit, named Christopher Scheiner, who was pro- 
fessor of mathematics at Ingolstadt, in imitation of Gali- 


leo had commenced a series of observations on them, but 
adopted the theory which, as we have seen, Galileo had 
examined and rejected, that these spots are planets cir- 
culating at some distance from the body of the sun. The 
same opinion had been taken up by a French astrono- 
mer, who in honor of the reigning family called them 
Borbonion stai's. Scheiner promulgated his notions in 
three letters, addressed to their common friend Welser, 
under the quaint signature oi '^ Apelles latens post tab- 
ulam,'^^ Galileo replied to Scheiner 's letters by three oth- 
ers, also addressed to Welser, and although the dispute 
was carried on amid mutual professions of respect and 
esteem, it laid the foundation of the total estrangement 
which afterwards took place between the two authors. 
Galileo's part of this controversy was published at Rome 
by the Lyncean Academy in 1613. To the last of his 
letters, \raten in December, 1612, is annexed a table of 
the expected positions of Jupiter's satellites during the 
months of March and April of the following year, which, 
imperfect as it necessarily w^as, cannot be looked upon 
without the greatest interest. 

In the same letter it is mentioned that Saturn present- 
ed a novel appearance, which, for an instant, almost in- 
duced Galileo to mistrust the accuracy of his earlier 
observations. The lateral appendages of this planet had 
disappeared, and the accompanying extract will show the 
uneasiness wliich Galileo could not conceal at the sight 
of this phenomenon, although it is admirable to see the 
contempt with which, even in that trying moment, he 
expresses his consciousness that his adversaries were un- 
worthy of the triumph they appeared on the point of 


celebrating. — '' Looking on Saturn within these few days, 
I found it solitary, without the assistance of its accus- 
tomed stars, and in short, perfectly round and defined 
like Jupiter, and such it still remains. Now what can 
be said of so strange a metamorphosis ? are perhaps the 
two smaller stars consumed, like the spots on the sun ? 
have they suddenly vanished and fled ? or has Saturn 
devoured his own children ? or was the appearance in- 
deed fraud and illusion, with which the glasses have for 
so long a time mocked me, and so many others who 
have often observed with me. Now perhaps the time is 
come to revive the withering hopes of those, who, guid- 
ed by more profound contemplations, have fathomed all 
the fallacies of the new observations and recognized 
their impossibility ! I cannot resolve what to say in a 
chance so strange, so new, and so unexpected ; the 
shortness of the time, the unexampled occurrence, the 
weakness of my intellect, and the terror of being mis- 
taken, have greatly confounded me." These first ex- 
pressions of alarm are not to be w-ondered at ; however, 
he soon recovered courage, and ventured to foretel the 
periods at which the lateral stars would again show them- 
selves, protesting at the same time, that he was in no 
respect to be understood as classing this prediction 
among the results w^hich depend on certain principles 
and sound conclusions, but merely on some conjectures 
which appeared to him probable. From one of the 
Dialogues on the System, we learn that this conjecture 
was, that Saturn might revolve upon his axis, but the 
period which he assumed is very different from the true 
one, as might be expected from its being intended to ac- 


count for a phenomenon of which Gahleo had not right- 
ly apprehended the chai^acter. 

He closed this letter with renewed professions of 
courtesy and friendship towards Apelles, enjoining Wel- 
ser not to communicate it widiout adding his excuses, if 
he should be thought to dissent too violently from his 
antagonist's ideas, declaring that his only object was the 
discovery of truth and that he had freely exposed his 
own opinion, which he was still ready to change, so 
soon as his errors should be made manifest to him; and 
that he would consider himself under special obhgation 
to any one who would be kind enough to discover and 
correct them. These letters were written from the 
villa of his friend Salviati at Selve near Florence^ where 
he passed great part of liis time, particulaiiy dui'ing his fre- 
quent indispositions, conceiving that the air of Florence 
was prejudicial to him. Cesi was very anxious for their 
appeai'ancej since they were (in his own words) so hard a 
morsel for the teeth of the Peripatetics, and he exhorted 
Galileo, in the name of the society, " to continue to give^ 
them, and the nameless Jesuit, somethins; to piaw." 



Letter to Christina^ Arch-Duchcss of Tuscany — Caccini — 
Galileo revisits Rome — Inchoffer — Problem of Longi- 

The uncompromising boldness with which Galileo pub- 
lished and supported his opinions, with httle regard to 
the power and authority of those who advocated the 
contrary doctrines, had raised against him a host of 
enemies, who each had objections to him pecuhar to 
themselves, but who now began to perceive the policy 
of uniting their strength in the common cause, to crush 
if possible so dangerous an innovator. All the professors 
of the old opinions, who suddenly found the knowledge 
on which their reputation was founded struck from under 
them, and who could not reconcile themselves to their 
new situation of learners, w^ere united against him ; and 
to this powerful cabal was now added the still greater 
influence of the Jesuits and pseudo-theological party, 
who fancied they saw in the spirit of Galileo's writings 
the same inquisitive temper which they had already 
found so inconvenient in Luther and his adherents. The 
alarm became greater every day, inasmuch as Gahleo 
had succeeded in training round him a numerous band of 
followers who all appeared imbued with the same dan- 
gerous spirit of innovation, and his favorite scholars 
were successful candidates for professorships in many of 
the most celebrated universities of Italy. 

At the close of 1613, Galileo addressed a letter to 


his pupil, the Abbe Castelli, in which he endeavored to 
show that there is as much difficulty in reconciling the 
Ptolemaic as the Copernican system of the world with 
the astronomical expressions contained in the Scriptures; 
and asserted, that the object of the Scriptures not being 
to teach astronomy, such expressions are there used as 
would be intelligible and conformable to the vulgar be- 
lief, without regard to the true structure of the universe ; 
wliich argument he afterwards amplified- in a letter ad- 
dressed to Christina, Grand Duchess of Tuscany, the 
mother of his patron Cosmo. He discourses on this 
subject with the moderation and good sense wliich so 
peculiarly characterized him. ''lam," says he, "in- 
clined to beheve, that the intention of the sacred Scrip- 
tures is to give to mankind the information necessary for 
their salvation, and which, surpassing all human knowl- 
edge can by no other means be accredited than by the 
mouth of the Holy Spirit. But I do not hold it necessa- 
ry to beheve, that the same God who has endowed us 
with senses, with speech, and intellect, intended that we 
should neglect the use of these, and seek by other 
means for knowledge w^hich they are sufficient to pro- 
cure us ; especially in ^a science hke astronomy, of 
which so Uttle notice is taken in the Scriptures, that 
none of the planets, except the sun and moon, and, 
once or twice only, Venus under the name of Lucifer, 
are so much as named there. Tliis therefore being gran- 
ted, methinks that in tlie discussion of natural prob- 
lems we ought not to begin at the authority of texts of 
Scripture, but at sensible experiments, and necessary 
demonstrations : for, from the divine word, the sacred 


Scripture and nature did both alike proceed, and I con- 
ceive that, concerning natural effects, that which either 
sensible experience sets before our eyes, or necessary 
demonstrations do prove unto us, ought not upon any 
account to be called into question, much less condemned, 
upon the testimony of Scriptural texts, which may under 
their words couch senses seemingly contraiy thereto. 

^' Again, to command the very professors of astro- 
nomy that they of themselves see to the confuting of 
their ow^n observations and demonstrations, is to enjoin a 
thing beyond all possibihty of doing; for it is not only to 
command them not to see that which they do see, and 
not to understand that which they do understand, but it 
is to order them to seek for and to find the contrar}' of 
that which they happen to meet with. I would entreat 
these wise and prudent fathers, that they would with all 
diligence consider the difference that is between opinion- 
ative and demonstrative doctrines ; to the end that well 
weighing in their minds with w^hat force necessary infer- 
ences urge us, they might the better assure themsekes 
that it is not in the power of the professors of demonstra- 
tive sciences to change their opinions at pleasure, and 
adopt first one side and then another ; and that there is a 
great ^difference between commanding a mathematician 
or a philosopher, and the disposing of a lawyer or a mer- 
chant ;' and that the demonstrated conclusions touching 
the things of natui^e and of the heavens cannot be chan- 
ged with the same facihty as the opinions are touching 
what is lawful or not in a contract, bargain, or bill of ex- 
change. Therefore, first let these men apply themselves 
to examine the arguments of Copernicus and others, and 


leave the condemnmg of them as erroneous and heretical 
to whom it belongeth ; yet let them not hope to find such 
rash and precipitous determinations in the wary and holy 
fathers, or in the absolute wisdom of him who cannot 
err, as those into which they suffer themselves to be 
hurried by some particular affection or interest of their 
own. In these and such other positions, which are not 
directly articles of faith, certainly no man doubts but 
His Holiness hath always an absolute power of admitting 
or condemning them, but it is not in the power of any 
creature to make them to be true or false, odierwise than 
of their o^vn nature, and in fact they are." We have 
been more particular in extracting these passages, be- 
cause it has been advanced by a writer of high reputation 
that the treatment which Galileo subsequG-'VJy experien- 
ced was solely in consequence of his persisting in the 
endeavor to prove that the Scriptures were reconcileable 
with the Copemican theory,* whereas we see here dis'^ 
tinctly that, for the reasons we have briefly stated, he 
regarded this as a matter altogether indifferent and be- 
side the question. 

Gahleo had not entered upon tliis discussion till driven 
to it by a most indecent attack, made on him from the 
pulpit, by a Dominican friar named Caccini, who thought 
it not unbecoming his habit or religion to play upon the 

* Ce philosophe (Galilee) ne fat point persecute comme bon astronome, 
mais comme mauvais theologien. C'est son entetement a vouloir concilier 
la Bible avec Copernic qui lui donna des juges. Mais vingt auteurs, surtout 
parmi les protestans, ont ecrit que Galilee fut persecute et imprisoone pour 
avoir sontenu que la terre tourne autour du soleil, que ce systeme a ete 
condanne par I'inquisition comme faux, errone et conti'aire a la Bible, &c. — 
Bergier Encyclopedic Methodique, Paris, 1790, Art. Sciences Humaines. 



words of a Scriptural text for the pui'pose of attacking j 
Galileo and his partisans with more personality. Galileo 

complained formally of Caccini's conduct to Luigi Ma- j 

rafH the general of the Dominicans, who apologised am- < 

ply to him, adding that he liimself was to be pitied for ' 

finding himself implicated in all the brutal conduct of ' 
thirty or forty thousand monks. 

In the mean lime, the inquisitors at Rome had taken \ 

the alarm, and were already, in 1615, busily employed in \ 

collecting evidence against Galileo. Lorini, a brother ' 

Dominican of Caccini, had given them notice of the : 

letter to Castelli of which we have spoken, and the ut- j 

most address was employed to get the original into their | 

hands, which attempt however was frustrated, as Castelli f 

had returned it to the writer. Caccini was sent for to \ 

Rome, settled there with the title of Master of the Con- | 

vent of St. Mary of Minerva, and employed to put the | 

depositions against Galileo into order. Galileo was not i 

at this time fully aware of the machniiations against him, J 
but suspecting something of their nature, he solicited and 
obtained permission from Cosmo, towards the end of 
1615, to make a journey to Rome, for the purpose of 

more directly confronting liis enemies in that city. There j 
was a rumor at the time that this visit was not voluntary, 

but that Galileo had been cited to appear at Rome. A | 

contemporary declares that he heard this from Galileo . 

himself: at any rate, in a letter wliich Galileo shortly •: 

afterwards wrote to Picchena, the Grand Duke's sec- - 

retary, he expresses lAmself well satisfied w4th the results I 
of this step, whether forced or not, and Querenghi thus 

describes to the Cardinal d' Este the public effect of his , 


appearance: ''Your Eminence would be delighted with 
Galileo if you heard him holding forth, as he often does, 
in the midst of fifteen or t^venty, all violently attacking 
him, sometimes in one house, sometimes in another. 
But he is armed after such a fashion that he laughs all of 
tliem to scorn — and even if the novelty of his opinions 
prevents entire persuasion, at least he convicts of empti- 
ness most of the arguments with which his adversaries 
endeavor to overwhelm him. He was particulary admi- 
rable on Monday last, in the house of Signor Frederico 
GhisiKeri ; and what especially pleased me was, that be- 
fore replying to the contraiy arguments, he amplified 
x-tnd enforced them with new grounds of great plausibiht)^, 
so as to leave his adversaries in a more ridiculous phght 
when he afterwards overturned them all." 

Among the malicious stories which were put into cir- 
culation, it had been said, that the Grand DuKe had 
withdrawn his favor, which emboldened many, who 
would not otherwise have ventured on such open oppo- 
sition, to declare against Galileo. His appearance at 
Rome, where he was lodged in the palace of Cosmo's 
ambassador, and whence he kept up a close correspon- 
dence with the Grand Duke's family, put an immediate 
stop to rumors of this kind. In htde more than a month 
he was apparently triumphant, so far as regarded himself; 
but the question now began to be agitated whether the 
whole system of Copernicus ought not to be condemned 
as impious and heretical. Galileo again urates to Pic- 
chena, " so far as concerns the clearing of my o^m char- 
acter, I might retui'n home immediately ; but aUhough 
this new question regards me no more than all those who 


for the last eighty years have supported these opinions 
both in public and private, yet, as perhaps I may be of 
some assistance in that part of the discussion which de- 
pends on the knowledge of truths ascertained by means 
of the sciences which I profess, I, as a zealous and 
Catholic Christian, neither can nor ought to withhold that 
assistance which my loiowledge affords; and this busi- 
ness keeps me sufficiently employed." De Lambre, 
whose readiness to depreciate Galileo's merit we have 
already noticed and lamented, sneeringly and ungi-ate- 
fully remarks on this part of his life, that '' it viras scarce- 
ly worth while to compromise his tranquility and reputa- 
tion, in order to become the champion of a truth which 
could not fail every day to acquire new partisans by the 
natural effect of the progress of enlightened opinions." 
We need not stop to consider what the natural effects 
might have been if none had at any time been found wha 
thought their tranquility worthily offered up m such a 

It has been hinted by several, and is indeed probable, 
that Gahleo's stay at Rome rather injured the cause (so 
far as provoking the inquisitorial censures could injure it) 
which it w^as his earnest desire to serve, for we cannot 
often enough repeat the assertion, that it was not the 
doctrine itself, so much as the free, unyielding manner in 
which it was supported, wliich was originally obnoxious. 
Copernicus had been allowed to dedicate his great work 
to Pope Paul III., and from the time of its fii'st appear- 
ance imder that sanction in 1543, to the year 1616, of 
which we ai'e now writing, this theory was left in the 
hands of mathematicians and pliilosophers, who alternate- 


ly attacked and defended it witliout receiving either sup- 
port or molestation from ecclesiastical decrees. But this 
was henceforward no longer the case, and a higher de- 
gree of importance was given to the controversy from 
the religious heresies which were asserted to be involved 
in the new opinions. We have already given specimens 
of the so called philosophical argmiients brought against 
Copernicus : and the reader may be curious to know the 
form of the theological ones. Those which we select 
are taken from a work, wliich indeed did not come forth 
till the time of Gahleo's third visit to Rome, but it is 
relative to the matter now before us, as it professed to be, 
and its author's party affected to consider it, a complete 
refutation of the letters to Castelli and the Archduchess 

It was the work of a Jesuit, Melcliior Inchoffer, and 
it was greatly extolled by his companions, ^' as differing 
so entirely from the pruiency of the Pnhagorean wri- 
tings." He quotes with approbation an author who, first 
referring to the first verse of Genesis for an argument 
that the earth was not created till after the heavens, ob- 
serv^es that the whole question is thus reduced to the 
examination of this purely geometrical difficulty — In the 
formation of a sphere, does the centre or circumference 
first come into existence ? If the latter (which we pre- 

* Tractatus Syllepticus. Romee, 1633. Tlie title-page of this remarka- 
ble production is decorated with an emblematical figure, representing theh 
earth included in a triangle; and in the thi*ee corners, grasping the globe wit 
their fore feet, are placed three bees, the arms of Pope Urban VIII. who 
condemned Galileo and his writings. The motto is *^ His fix a quiescit,^^ 
" Fixed by these it is at rest." 


sume Melchior's friend found good reason for deciding 
upon) , the consequence is inevitable. The earth is in 
the centre of the universe. 

It may not be unprofitable to contrast the extracts 
which we have given from Galileo's letters on the same 
subject with the following passage, which appears one of 
the most subtle and argumentative which is to be found 
in Melchlor's book. He professes to be enumerating and 
refuting the principal arguments which the Copernicans 
adduced for the motion of the earth. '' Fifth argument. 
Hell is in the centre of the earth, and in it is a fire tor- 
menting the damned ; therefore it is absolutely necessary 
that the earth is movable. The antecedent is plain." 
(Inchoffer then quotes a number of texts of Scripture, on 
which, according to him, the Copernicans relied in proof 
of this part of the argument.) '' The consequent is prov- 
ed : because fire is the cause of motion, for which rea- 
son Pythagoras, who, as Aristotle reports, puts the place 
of punishment in the centre, perceived that the earth is 
animate and endowed with action. I answer, even al- 
lowing that hell is in the centre of the earth, and a fire 
in it, I deny the consequence: and for a proof I say, if 
the argument is worth any tiring, it proves also that 
lime-kilns, ovens, and fire grates are animated and spon- 
taneously movable. I say, even allomng that hell is in 
the centre of the earth : for Gregory, book 4, dial. chap. 
42, says, that he dare not decide rashly on this matter, 
although he thinks more probable the opinion of those 
who say that it is under the earth. St. Thomas, in 
Opusc. 10, art. 31, says: Where hell is, whether in the 
centre of the earth or at the surface, does not in my 


opiiiion^ relate to aiiy ai'ticie of faith; and it is superfu- 
0U3 to be solicitous about such things, either in asserting 
or denying them. And Opusc. 11, art. 24, he says, 
that it seems to him that nothing should be raslily as- 
serted on this matter, particularly as Augustin thinks that 
nobody loiows where it is; but I do not, says he, think 
that it is in the centre of the earth. I should be loth^ 
however, that it should be hence inferred by some people 
that hell is in the eai'th, that we are ignorant where hell 
is, and therefore that the situation of the earth is also 
unknown, and, in conclusion, that it cannot therefore be 
the centre of the universe. The ai'guraent shall be re- 
torted in another fashion: for if the place of the eailh is 
tuiknowTi, it cannot be said to be in a great circle, so as 
to be moved round the sun. Finally I say that in fact 
it is kno\^Ti where the earth is." 

It is not impossible that some persons adopted the 
Copernican theory, from an affectation of singularity and 
freethinking, without being able to give very somid rea- 
sons for their change of opinion, of whom we have an 
instance in Origanus, the astrological instructor of Wal- 
lenstein's famous attendant Seni, who edited his work. 
His arguments in favor of the earth's motion are quite 
on a level with those advanced on the opposite side in 
favor of its immobihtj^; but we have not found any traces 
wlmtever of such absurdities as these having been urged 
by any of the leaders of that pai'ty, and it is far more 
probable that they are the creatures of Melchior's own 
imagination. At any rate it is worth remarking how 
completely he disregards the real physical arguments, 
j which he ought, in justice to his. cause, o have attempt- 


ed to controvert. His book was aimed at Galileo and 
his adherents, and it is scarcely possible that he could 
seriously persuade himself that he was stating and over- 
turning arguments similar to those by which Galileo had 
made so many converts to the opinions of Copernicus. 
Whatever may be our judgment of his candor, we may 
at least feel assured that if this had indeed been a fair 
specimen of Galileo's philosophy, he might to the end of 
his hfe have taught that the earth moved round the sun, 
or if his fancy led him to a different hypothesis, he 
might like the Abbe Baliani have sent the earth spinning 
round the stationary moon, and hke him have remained 
unmolested by pontifical censures. It is true that Bali- 
ani owned his opinion to be much shaken, on observing 
it to be opposed to the decree of those in whose hands 
was placed the power of judging articles of faith. But 
Galileo's uncompromising spirit of analytical investiga- 
tion, and the sober but invmcible force of reasoning with 
which he beat down every sophism opposed to him, the 
instruments with which he worked, were more odious 
than the work itself, and the condemnation wliich he had 
vainly hoped to avert was probably on his very account 

Galileo, according to his o^vn story, had in March 
1616 a most gracious audience of the pope, Paul V,, 
which lasted for nearly an hour, at the end of which his 
holiness assured him, that the Congregation were no 
longer in a humor to listen lightly to calumnies against 
him, and that so long as he occupied the papal chair, Gal- 
ileo might think himself out of all danger. But neverthe- 
less he was not allowed to return home, without receiving 


formal notice not to teach the opmions of Copernicus, 
that the sim is in the centre of the system, and that the 
earth moves about it, from that time orward, in any 
manner. That these were the hteral orders given to 
Galileo will be presently proved from the recital of them 
in the famous decree against him, seventeen years later. 
For the present, his letters which we have mentioned, 
as well as one of a similar tendency by Foscarmi, a 
Carmehte friar — a commentary on the book of Joshua 
by a Spaniai'd named Diego Zuniga — Kepler's Epitome 
of the Copemican Theory^ — and Copernicus' own work, 
were inserted in the hst of forbidden books, nor was it 
till four years afterwards, in 1620, that, on reconsidera- 
tion, Copernicus was allowed to be read with certain 
omissions and alterations then decided upon. 

Galileo quVt^d Rome scarcely able to conceal his 
contempt and ihdignation. Two years afterwards this 
spirit had but little subsided^^ in forwarding to the 
Archduke Leopold his Theory of the Tides, he accom- 
panied it with the following remarks: — '' This theory oc- 
curred to me when in Rome, whilst the theologians were 
debating on the prohibition of Copernicus' book, and of 
the opinion maintained in it of the motion of the earth, 
which I at that time believed; until it pleased those gen- 
tlemen to suspend the book, and declai^e the opinion 
false and repugnant to the holy scriptm'es. Now, as I 
know how well it becomes me to obey and beheve the 
decisions of my superiors, which proceed out of more 
profoujad knowledge than the weakness of my intellect 

* Kepler's Epitome was not published till 1619 ; it was then inserted in 
the Index. 


call attain to, this theory which I send you, which is i 
founded on the motion of the earth, 1 now look upon as j 
a fiction and a dream, and beg your highness to receive | 
it as such. But, as poets often learn to prize the crea- \ 
tions of their fancy, so, in Hke manner, do I set some S 
value on this' absurdity of mine. It is true that when I ; 
sketched this little work, I did hope that Copernicus '^ 
would not, after 80 years, be convicted of error, and I ') 
had intended to develope and amplify it farther, but a I 
voice from heaven suddenly awakened me, and at once f 
amiihilated all my confused and entangled fancies." I 

It might have been predicted, from the tone of this *| 
letter alone, that it would not be long before Galileo i 
would again bring himself under the censuring notice of 
the astronomical hierarchy, and indeed he had, so early 
as 1610, collected some of the materials far the work 
which caused the final explosion, and on which he now 
employed himself with as little intermission as the weak 
state of his health permitted. 

He had been before this thne engaged in a corres- 
pondence with the court of Spain, on the method of 
observing longitudes at sea, for the solution of which ' 
important problem Philip III. had offered a considerable ' 
reward, an example which has since been followed in '■ 
our owTi and other countries. Galileo had no sooner ■ 
discovered Jupiter's satellites, then he recognized the ^ 
use which might be made of them for that purpose, and ^ 
devoted himself with peculiai' assiduit}^ to acquiring as ' 
perfect a knowledge as possible of their revolutions. ' 
The reader will easily understand how they were to be ^ 
used, if their motion could be so well ascertained as to « 


enable Galileo at Florence to predict the exact times at 
which any remarkable configm'ations would occur, as, 
for mstance, the times at which any one of them would 
be eclipsed by Jupiter. A maiiner who in the middle 
of die Atlantic should observe the same eclipse, and 
compai'e the time of night at which he made the obser- 
vation (wliich he'might know by setting his watch by the 
sun on the preceding day) with the time mentioned in 
the predictions, would, from the difference between the 
two, learn the difference between the hour at Florence 
and the hour at the place where the ship at that time 
happened to be. As the earth tui'ns uniformly round 
dii'ough 360^ of longitudes in 24 houi's, that is, tlirough 
15° in each hour, the hours, minutes, and seconds of 
time which express this difference must be multiplied by 
15, and the respective products will give the degrees, 
minutes, and seconds of longitude, by wliich the ship 
was dien distant from Florence. This statement is 
merely intended to give those who are unacquainted with 
astronomy, a general idea of the manner in which it was 
proposed to use these satellites. Our moon had ah'eady 
been occasionally employed in the same way, but the 
; comparative frequency of the eclipses of Jupiter's moons, 
iand the suddenness with which they disappear, gives a 
' decided advantage to the new method. Both methods 
were embarrassed by the difficulty of observing the 
\ eclipses at sea. In addition to this, it was requisite, in 
1 1 both methods, that the sailors should be provided with 
accurate means of knowing the hour, wherever they might 
'chance to be, which was far from being the case, for al- 
though (in order not to mterrupt the explanation) we 


have above spoken of their watches^ yet the watches and 
clocks of that day were not such as could be relied on 
sufficiently, during the interval which must necessai'ily 
occur between the two observations. This considera- 
tion led Galileo to reflect on the use which might be 
made of his pendulum for this purpose; and, with res- 
pect to the other difficulty, he contrived a peculiar kind 
of telescope, with which he flattered himself, somewhat 
prematurely, that it would be as easy to observe on ship- 
board as on shore. 

During his stay at Rome, in 1615, and the following 
year, he disclosed some of these ideas to the Conte di 
Lemos, the viceroy of Naples, who had been president 
of the council of the Spanish Indies, and was fully aware 
of the importance of the matter. Galileo was in conse- 
quence invited to communicate directly with the Duke •' 
of Lerma, the Spanish minister, and instructions were 
sent by Cosmo, to the Conte Orso d'Elci, his ambassa- 
dor at Madrid, to conduct the business there. Galileo 
entered warmly into the design, of which he had no other ! 
means of verifying the practicability ; for as he says I 
in one of his letters to Spain — '•' Your excellency may ) 
well believe that if this were an undertaking which I i 
could conclude by myself, I would never have gone a- - 
bout begging favors from others ; but in my study there ^ 
are neither seas, nor Indies, nor islands, nor ports, nor ; 
shoials, nor ships, for w^hich reason I am compelled to * 
share the enterprise with great personages, and to fatigue 
myself to procure the acceptance of that, which ought | 
witli eagerness to be asked of me ; but I console myself j 
with the reflection that I am not singular in this, but that ! 


it commonly happens, with the exception of a little repu- 
tation, and that too often obscured and blackened by 
envy, that the least part of the advantage falls to the 
share of the inventors of things, which afterwards bring 
great gain, honors, and riches to others ; so that I will 
never cease on my part, to do every thing in my power, 
and I am ready to leave here all my comforts, my comi- 
try, my friends, and family, and to cross over into Spain 
to stay as long as I may be wanted in Se\ille, or ^^is- 
bon, or wherever it may be convenient, to implant the 
knowledge of this method, provided that due assistance 
and dihgence be not wanting on the part of those who 
are to receive it, and who should solicit and foster it." 
But he could not, with all his enthusiasm., rouse the at- 
tention of the Spanish court. The negotiation languish- 
ed, and although occasionally renewed during the next 
ten or twelve years, was never brought to a satisfactory 
issue. Some explanation of this otherwise unaccount- 
able apathy of the Spanish court, with regard to the 
solution of a problem which they had certainly much at 
heart, is given in NelH's life of Galileo ; where it is 
asserted, on the authorit}^ of the Florentine records, 
that Cosmo required privately from Spain, (in return for 
the permission granted for Galileo to leave Florence, in 
pursuance of this design,) the privilege of sending every 
year from Leghorn two merchantmen, duty free, to the 
Spanish Indies. 



Controversy on Comets — Saggiatore — Galileo'' s reception 
by Urban VllL — His family. 

The year 1618 was remarkable for the appearance of 
three comets, on which almost every astronomer in 
Europe found something to say and wTite. Galileo pub- 
lished some of his opinions with respect to them, through 
the medium of Mario Guiducci. This astronomer de- 
livered a lecture before the Florentine academy, the 
heads t)f which he was supposed to have received from 
Galileo, who during the whole time of the appear- 
ance of these comets, was confined to his bed by severe 
illness. This essay was printed in Florence at the sign 
of The Medicman Stars, What principally deserves 
notice in it, is the opinion of Galileo, that the distance 
of a comet cannot be safely determined by its pirallax, 
from which we learn that he inclined to believe that com- 
ets are nothing but meteors occasionally appearing in the 
atmosphere, like rainbows, parhelia, and similar phenom- 
ena. He points out the difference in this respect be- 
tween a fixed object, the distance of which may be cal- 
culated from the difference of direction in which two 
observers (at a known distance from each other) are 
obliged to turn themselves in order to see it, and meteors 
like the rainbow, which are simultaneously formed in 
different drops of water for each spectator, so that two 
observers in different places are in fact contemplating dif- 
iferent objects. He then warns astronomers not to 


engage with too much warmth in a discussion on the 
distance of comets before they assure themselves to 
which of these two classes of phenomena they are to be 
referred. The remark is in itself perfectly just, al- 
though the opinion which occasioned it is now as cer- 
tainly known to be erroneous, but it is questionable 
whether the observations which, up to that time, had 
been made upon comets, were sufficient, either in num- 
ber or quality, to justify the censure which has been cast 
on Gahleo for his opinion. The theory, moreover, is 
merely introduced as an hypothesis in Guiducci's essay. 
The same opinion was for a short time embraced by 
Cassini, a celebrated Italian astronomer^ invited by Lou- 
is XIV. to the Observatory at Paris, when the science 
was considerably more advanced, and Newton, in his 
principiaj did not think it unworthy of him to show on 
what grounds it is untenable. 

Galileo was become the object of animosity in so 
many quarters that none of his pubhshed opinions, wheth- 
er correct or incorrect, ever wanted a ready antagonist. 
The champion on the present occasion was again a Je- 
suit ; his name was Oratio Grassi, who pubhshed The 
•Astronomical and Philosophical Balance^ under the dis- 
guised signature of Lotario Sarsi. 

Galileo and his friends were anxious that his reply to 
Grassi should appear as quickly as possible, but his 
health had become so precarious, and his frequent illness- 
es occasioned so many interruptions, that it was not 
until the autumn of 1623 that II Saggiatore (or The As- 
say er) as he called his answer, was ready for publication. 
This was printed by the Lyncean Academy, and as 


Cardinal Maffeo Barberino, who had just been elected 
Pope, (with the title of Urban VIII.) had been closely 
connected with that society, and was also a personal 
friend of Cesi and of Galileo, it was thought a prudent 
precaution to dedicate the pamphlet to him. This essay 
enjoys a peculiar reputation among Gahleo's works, not 
only for the matter contained in it, but also forlbe style 
in which it is written; insomuch that Andres, eulogizing 
Galileo as one of the earhest who adorned philosophical 
truths with the graces- and ornaments of language, ex- 
pressly instances the Saggiatore, which is also quoted by 
Frisi and Algarotti, as a perfect model of this sort of 
composition. In the latter particular, it is unsafe to 
interfere .with the decisions of an Italian critic; but with 
respect to its substance, this famous composition scarce- 
ly appears to deserve its preeminent reputation. It is a 
prglix and rather tedious examination of Grassi's Essay; 
nor do the arguments seem so satisfactory, nor the rea- 
sonings so compact as is generally the case in Galileo's 
other writings. It does however, like all his other 
works, contain many very remarkable passages, and the 
celebrity of this production requires that we should ex- 
tract one or two of the most characteristic. 

The first, though a very short one, will serve to show 
the tone which Galileo had taken with respect to the 
Copernican system since its condemnation at Rome, in 
1616. ''In conclusion, since the motion attributed to 
the earth, which I, as a pious and Catliolic person, con- 
sider most false, and not to exist, accommodates itself 
so well to explain so many and such different phenom- 
ena, I shall not feel sure, unless Sarsi descends to more 


distinct considerations than those which he has yet pro- 
duced, that, false as it is, it may not just as deludingly 
correspond with the pheomena of comets." 

Sarsi had quoted a story from Suidas in support of his 
argument that motion ahvays produces heat, how the 
Babylonians used to cook their eggs by whirhng them in 
a sling : to which Galileo rephes : ' ' I cannot refrain 
from marvelling that Sarsi will persist in proving to 
me, by authorities, that which at any moment I can 
bring to the test of experiment. We examine witnesses 
in diings which are doubtful, past, and not permanent, 
but not in those things which are done in our own pres- 
ence. If discussing a difficult problem were like carry- 
ing a weight, since several horses will carry more sacks 
of corn than one alone will, I would agree that many 
reasoners avail more than one; but discoursing is like 
coursingj and not like carrying, and one barb by himself 
will run farther than a hundred Friesland horses. When 
Sarsi brings up such a multitude of authors, it does not 
seem to me that he in the least degree strengthens his 
own conclusions, but he ennobles, the cause of Signor 
Mario and myself, hy showing that we reason better than, 
many men of established, reputation. If Sarsi insists 
that I beUeve, on Suidas* credit, that the Babylonians 
cooked eggs by swiftly whirling them in a sling, I will 
believe it] but I must needs say, that the cause of such 
an effect is very remote from that to which it is attrib- 
uted, and to find the true cause I shall reason thus. If 
an effect does not follow with us which followed with 
others at aiiother trme, it is because, in our experiment^ 
something is: waiiting which was the cause of the former 
a 2 


success; and if only one thing is wanting to us, that one 
thing is the true cause. Now we have eggs, and slings, 
and strong men to whirl them, and yet they will not be- 
come cooked; nay, if they were hot at first, they more 
quickly become cold: and since nothing is wanting to 
us but to be Babylonians, it follows that being Babyloni- 
ans is the true cause why the eggs became hard, and not 
the friction of the air, which is what I wish to prove. — 
It is possible that in traveling post, Sarsi has never no- 
ticed what fresliness is occasioned on the face by the 
continual change of air; and if he has felt it, will he 
rather trust the relation by others, of what was done two 
thousand years ago at Babylon, than what he can at this 
moment verify in his own person? I at least will not be 
so wilfully wrong, and so ungrateful to nature and to 
God, that having been gifted with sense and language, I 
should voluntarily set less value on such great endow- 
ments than on the fallacies of a fellow man, and bhndly 
and blunderingly believe whatever I hear, and barter the 
freedom of my intellect for slavery to one as liable to 
error as myself." 

Our final extract shall exhibit a sample of Galileo's 
metaphysics, in wliich may be observed the germ of a 
theory very closely allied to that which was aften^'ards 
developed by Locke and Berkeley. — '^ I have now only 
to fulfil my promise of declaring my opinions on the 
proposition that motion is the cause of heat, and to ex- 
plain in what manner it appears to me that it may be 
true. But I must first make some remarks on that 
which we call heat, since I strongly suspect that a no- 
tion of it prevails which is very remote from the truth; 


for it is believed that there is a true accident, aiFection, 
arid quality, really inherent in the substance by which 
we feel ourselves heated. This much I have to say, that 
so soon as I conceive a material or corporeal substance, 
I simultaneously feel the necessity of conceiving that it 
has its boundaries, and is of some shape or other; that, 
relatively to others, it is great or small; that it is in this 
or that place, in this or that time; that it is in motion, 
or at rest; that it touches, or does not touch another 
body; that it is unique, rare, or common; nor can I, by 
any act of the imagination, disjoin it from these quali- 
ties: but I do not find myself absolutely compelled to 
apprehend it as necessarily accompanied by such con- 
ditions, as that it must be white or red, bitter or sweet, 
sonorous or silent, smelling sweetly or disagreeably; and 
if the sense had not pointed out these qualities, it is 
probable that language and imagination alone could never 
have arrived at them. Because, I am inclined to think 
that these tastes, smells, colors, &c., with regard to the 
subject in which they appear to reside, are nothing more 
than mere names, and exist only in the sensitive body; 
insomuch that, when the living creature is removed, all 
these qualities are carried off and annihilated; although 
we have imposed particular names upon them, and dif- 
ferent from those of the other first and real accidents, 
and would fain persuade ourselves that they are truly 
and in fact distinct. But I do not beheve that there ex- 
ists any thing in external bodies for exciting tastes, 
smells, and sounds, but size, shape, quantity, and mo- 
tion, swift or slow; and if ears, tongues, and noses were 
removed, I am of opinion that shape, number, and mo- 


tion would remain, but there would be an end of smells, i 
tastes, and sounds, which, abstractedly from the living i 
creature, I take to be mere words." 

In the spring following the publication of the '' Saggi- ! 
atore," that is to say, about the time of Easter, in 1624, | 
Galileo went a third time to Rome to compliment Urban j 
on his elevation to the pontifical chair. He was obliged j 
to make this journey in a litter; and it appears from his i 
letters that for some years he had been seldom able to \ 
bear any other mode of conveyance. In such a state of I 
health it seems unlikely that he would have quitted | 
home on a mere visit of ceremony, which suspicion is ' 
strengthened by the beginning of a letter from him to , 
Prince Cesi, dated in October, 1623, in which he says: ' 
'^I have received the very courteous and prudent advice ( 
of your excellency about the time and manner of my j 
going to Rome, and shall act upon it: and I will visit 
you at Acqua Sparta, that I may be completely in- 
formed of the actual state of things at Rome." How- 
ever this may be, nothing could be more gratifying than 
his public reception there. His stay in Rome did not 
exceed two months, (from the beginning of April till 
June,) and during that time he was admitted to six long 
and satisfactory interviews with the Pope, and on his 
departure received the promise of a pension for his son 
Vincenzo, and was himself presented w^th " a fine paint- 
ing, two medals, one of gold, the other of silver, and a 
good quantity of agnus dei." He had also much com^ 
munication with several of the cardinals, one of whom. 
Cardinal Hohenzoller, told him that he had represented 
to the pope on the subject of Copernicusj that '^all the 


heretics were of that opinion, and considered it as un- 
doubted; and that it would be necessary to be very 
circumspect in coming to any resolution : to which his 
holiness replied, that the church had not condemned it, 
nor was it to be condemned as heretical, but only as 
rash; adding, that there was no fear of any one under- 
taking to prove that it must necessarily be true." Urban 
also addressed to Ferdinand, who had succeeded his 
father Cosmo as Grand Duke of Tuscany, expressly for 
the purpose of recommending Galileo to him. '^For 
We find in him not only hterary distinction, but also the 
love of piety, and he is strong in those qualities by 
which pontifical good-will is easily obtained. And now, 
when he has been brought to this city to congratulate 
Us on Our elevation. We have very lovingly embraced 
him; — nor can We suffer him to return to the country 
whither your liberality recalls him without any ample 
provision of pontifical love. And that you may know 
how dear he is to Us, We have willed to give him this 
honorable testimonial of virtue and piety. And We 
further signify thai every benefit which you shall confer 
upon him, imitating, or even surpassing your father's lib- 
erality, will conduce to Our gratification." Honored 
with these unequivocal marks of approbation, Galileo 
returned to Florence, 

His son Vincenzo is soon afterwards spoken of as be- 
ing at Rome ; and it is not improbable that Galileo sent 
I him thither on the appointment of his friend and pupil, 
I the Abbe Castelli, to be mathematician to the pope. 
Vincenzo had been legitimated by an edict of Cosmo in 
1 1619, and, according to Nelli, married, in 1624, Ses- 


tilia, the daughter of Carlo Bocchineri. There are no 
traces to be found of Vincenzo's mother after 1610, 
and perhaps she died about that time. Galileo's family 
by her consisted of Vincenzo and two daughters, Julia 
and Polissena, who both took the veil in the convent of 
Saint Matthew at Arcetri, under the names of Sister 
Arcangiola and Sister Maria Celeste. The latter is said 
to have possessed extraordinary talents. The date of 
Vincenzo's marriage, as given by Nelli, appears some- 
what inconsistent wdth the correspondence between Gali- 
leo and CasteUi, in which, so late as 1629, Galileo is 
•apparently writing of liis son as a student under CastelH's 
superintendence, and intimates the amount of pocket- 
money he can afford to allow him, which he fixes at three 
crowns a month ; adding, that '' he ought to be content- 
edf with as many crowns, as, at his age, I possessed t; 
groats." CasteUi had given but an unfavorable account i 
of y iiTcenzo's conduct, characterizing him as '' dissolute, 
obstinate, and impudent ; " in consequence of which be- | 
haviour, Gahleo seems to have thought that the pension 
of sixty crowns, which had been granted by the pope, 
might be turned to better account than by employing it 
on his son's education ; and accordingly in his reply he 
requested CasteUi to dispose of it, observing that the 
proceeds would be useful in assisting him to discharge a 
great load of debt with which he found himself saddled 
on account of his brother's family. Besides tliis pension 
another of one hundred crowns was in a few years gran- 
ted by Urban to Gahleo himself, but it appears to have 
been very irregularly paid, if at aU. 


About the same time Galileo found himself menaced 
either with the deprivation of his stipend as extraordinary 
professor at Pisa, or with the loss of that leisure which, 
on his removal to Florence, he had been so anxious to 
secure. In 1629, the question was agitated by the party 
opposed to him, whether it were in the power of the 
grand duke to assign a pension out of the funds of the 
University, arising out of ecclesiastical dues, to one who 
neither lectured nor resided there. This scruple had 
slept during nineteen years which had elapsed since Gal- 
ileo's establishment in Florence, but probably those who 
now raised it reckoned upon finding in Ferdinand II., 
then scarcely of age a less firm supporter of Galileo than 
his father Cosmo had been. But the matter did not pro- 
ceed so far ; for, after full deliberation, the prevalent 
opmion of the theologians and jurists who were consulted 
appeared to be in favor of this exercise of prerogative, 
and accordingly Galileo retained his stipend and privi- 


Publication of Galileo's Si/stem of the world^ — His Con- 
demnation and Abjuration. 

In the y^ar 1620, Galileo brought to its conclusion his 
[great work, ^' Dialogue on the Ptolemaic and Copemi- 


can Systems," and began to take the necesary steps for 
procuring permission to print it. This was to be obtain- 
ed in the first instance from an officer at Rome, entitled 
the master of the sacred palace ; and after a little negoti- 
ation Galileo found it would be necessary for him to re- 
turn thither, as his enemies were still busy in thwarting 
his views and wishes. Niccolo Riccardi, who at that 
time filled the office of master of the palace, had been a 
pupil of Galileo, and was well disposed to facilitate his 
plans ; he pohited out, however, some expressions in the 
work which he thought it necessary to erase, and, with 
the understanding that this should be done, he returned 
the manuscript to Galileo with his subscribed approbation. 
The unhealthy season was drawing near, and Galileo, 
unwilling to face it, returned home, where he intended to 
complete the index and dedication, and then to send it 
back to Rome to be printed in that city, under the su- 
perintendence of Federigo Cesi. This plan was discon- 
certed by the premature death of that accompUshed no- 
bleman, in August 1630, in whom Galileo lost one of 
his steadiest and most effective friends and protectors. 
This unfortunate event determined Galileo to attempt to 
procure permission to print his book at Florence. A 
contagious disorder had broken out in Tuscany with 
such severity as almost to interrupt all communication 
between Florence and Rome, and this was ui^ged by 
Galileo as an additional reason for granting his request. 
Riccardi at first seemed inclined to insist that the book 
should be sent to him a second time, but at last content- 
ed himself with inspecting the commencement and con- 
clusion, and consented that (on its receiving also a license 


from the inquisitor-general at Florence, and from one or 
two others whose names appear on the title-page) it 
might be printed where Galileo wished. 

These protracted negotiations prevented the publica- 
tion of the work till late in 1632 ^it then appeared, with 
a dedication to Ferdinand, under the following title :-^ 
''A Dialogue, by Galileo Galilei, Extraordinary Mathe- 
matician of the University of Pisa, and Principal Philos- 
opher and Mathematician of die Most Serene Grand 
Duke of Tuscany ; in which, in a conversation of four 
days, are discussed the two principal Systems of the 
World, the Ptolemaic and Copernican, indeterminately 
proposing the Philosohical Arguments as well on one 
side as on the other." The beginning of the introduc- 
tion, which is addressed '' To the discreet Reader," is 
much too characteristic to be passed by v/ithout notice. 
— " Some years ago, a salutary edict was promulgated 
at Rome, which, in order to obviate the perilous scan- 
dals of the present age, enjoined an opportune silence on 
the Pythagorean opinion of the earth's motion. Some 
were not wanting, who rashly asserted that this decree 
originated, not in a judicious examination, but in ill in- 
formed passion ; and complaints were heard that counsel- 
lors totally inexperienced in astronomical observations 
ought not by hasty prohibitions to clip the wings of spec- 
ulative minds. My zeal could not keep silence when I 
heard these rash lamentations, and I thought it proper, as 
being fully mformed with regard to that most prudent de- 
termination, to appear publicly on the theatre of the 
world as a witness of tbe actual truth. I happened at 

I ^^^ 



that time to be in Rome ; I was admitted to the audien- 
ces, and enjoyed the approbation of the most eminent 
prelates of that court ; nor did the pubHcation of that 
decree occur witliout my receiving some prior intimation 
of it.^ Wherefore it is my intention in this present work 
to show to foreign nations that as much is known pr this 
matter in Italy, and pai'ticularly in Rome, as ultrafhontane 
diligence can ever have formed any notion of, and col- 
lecting together all my own speculations on the Coperni- 
can system, to give them to miderstand that the know- 
ledge of all these preceded the Roman censures, and 
that from this country proceed not only dogmas for the 
salvation of the soul, but also ingenious discoveries for 
the gratification of the understanding. With this object, 
I have taken up in the Dialogue the Copernican side of 
the question, treating it as a pure mathematical hypothe- 
sis : and endeavoring in every aitificial manner to repre- 
sent it as having the advantage, not over the opinion of 
the stability of the earth absolutely, but according to the 
mamier in which that opinion is defended by some, who 
indeed profess to be Peripaterics, but retain only the 
name, and are contented without improvement to worship 
shadows, not philosophizing with their own reason, but 
only from the recollection of four principles imperfectly 
understood." — This very flimsy veil could scarcely blind 
,any one as to Galileo's real views in composing this work, 
nor does it seem probable that he framed it with any ex- 

*Delambre quotes this sentence from a passage which is so obviously iron- 
ical tliroughout, as an instance of Galileo's mis-statement of facts ! — Hist 
deVAatr, Mod, vol. i. p. 666. 


pectation of appearing neutral in the discussion. It is 
more likely that he flattered himself that, under the new 
goverment at Rome, he was not hkely to be molested on 
account of the personal prohibition which he had receiv- 
ed in 1616, " not to beheve or teach the motion of the 
earth in any maimer," provided he kept himself within 
the letter of the limits of the more public and general 
order, that the Copernican system was not to be brought 
forward otherwise than as a mere mathematically con- 
venient, but in fact unreal supposition. So long as this 
decree remained in force, a due regard to consistency 
w^ould compel the Roman Inquisitors to notice an une- 
quivocal violation of it ; and this is probably what Urban 
had imphed in the remark quoted by HohenzoUer to 
Galileo. There were not wanting circumstances which 
might compensate for the loss of Cosmo and of Federi- 
go Cesi ; Cosmo had been succeeded by his son, who, 
though he had not yet attained his father's energy, show- 
ed himself as friendly as possible to Galileo. Cardinal 
Bellarmine, who had been mainly instrumental in procu- 
ring the decree of 1616, was dead ; Urban on the con- 
trary, who had been among the few Cardinals who then 
opposed it as uncalled for and ill-advised, was now pos- 
sessed of supreme power, and his recent affability seemed 
to prove that the increased difference in their stations 
had not caused him to forget their early and long-contin- 
ued intimacy. It is probable that Galileo would not 
have found himself mistaken in this estimate of his posi- 
tion, but for an unlucky circumstance, of which his eni- 
mies immediately saw the iipportance, and which they 


were not slow in making available against him. The 
dialogue of Gahleo's work is conducted between three 
personages ; — Salviati and Sagredo, who were two noble- 
men, friends of Galileo, and Simphcio, a name borrow- 
ed from a noted commentator upon Aristotle, who wrote 
in the sixth century. Salviati is the principal philoso- 
pher of the work; it is to him that the others apply for so- 
lutions of their doubts and difficulties, and on him the prin- 
cipal task falls of explaining the tenets of the Coperni- 
can theory. Sagredo is only a half convert, but an acute 
and ingenious one ; to him are allotted the objections 
which seem to have some real difficulty in them, as well 
as lively illustrations and digressions, which might have 
been thought inconsistent with the gravity of Salviati 's 
character. Simplicio, though candid and modest, is of 
course a confirmed Ptolemaist and Aristotehan, and is 
made to produce successively all die popular arguments 
of that school in support of his master's system. Placed 
between the wit and the philosopher, it may be guessed 
tliat his success is very indifferent, and in fact he is al- 
ternately ridiculed and confuted at every turn. As Gah- 
leo racked his memory and invention to leave unanswer- 
ed no argument which was or could be advanced against 
Copernicus, it unfortunately happened, that he introduced 
some which Urban him_self had urged upon him in their 
former controversies on this subject ; and Galileo's oppo- 
nents found means to make His Holiness beheve that the 
character of Simplicio had been sketched in personal de- 
rision of him. We do not think it necessary to exoner- 
ate Galileo from this charge ; the obvious folly of such 
an useless piece of ingratitude speaks sufficiently for itself. 


But self-love is easily irritated ; and Urban, who aspired 
to a reputation for literature and science, was peculiarly 
sensitive on this point. His own expressions almost 
prove his belief that such had been Galileo's design, and 
it seems to explain the otherwise inexplicable change 
which took place in his conduct towards his old friend, 
on account of a book which he had himself undertaken to 
examine, and of which he had authorised the publication. 
One of the eariiest notices of what was approaching, 
is found in the dispatches dated August 24, 1632, from 
Ferdinand's minister, Andrea Cioli, to Francesco Nico- 
lini; the Tuscan ambassador at the court of Rome. 

" I have orders to signify to Your Excellency that His 
Highness remains greatly astonished that a book, placed 
by the author himself in the hands of the supreme au- 
thority at Rome, read and read again there most attent- 
ively, and in which every thing, not only with the con- 
sent, but at the request of the author, was amended, al- 
tered, added, or removed at the will of his superiors, 
which was again subjected here to the same examination, 
agreeably to orders from Rome, and which finally was 
licensed both there and here, and here printed and pub- 
lished, should now become an object of suspicion at the 
end of two years, and the author and printer be prohib- 
ited from publishing anymore." — In the sequel is inti- 
mated Ferdinand's desire that the charges, of whatever 
nature they might be, either against Galileo or his book, 
might be reduced to writing and forwarded to Florence, 
jl that he might prepare for his justification ; but this rea- 
sonable demand was utterly disregarded. It appears to 


have been owing to the mean subserviency of Cioli to 
the court of Rome, that Ferdinand refrained from inter- 
fering more strenuously to protect Galileo. Cioh's words 
are : ''- The Grand Duke is so enraged with this business 
of Galileo, that I do not know what will be done. I 
know, at least, that His Holiness shall have no reason to 
• complain of his ministers, or of their bad advice." 

A letter from Galileo's Venetian friend, Micanzio, da- 
ted about a month later, is in rather a bolder and less 
formal style : — ''The efforts of your enemies to get 
your book prohibited will occasion no loss either to 
your reputation, or to the intelligent part of the world. 
- As to posterity, this is just one of the surest ways to 
^hand thebook down to them. But what a wretched set 
this must be to whom every good thing, and all that is 
founded in natui'e, necessarily appears hostile and odi- 
ous ! The world is not restricted to a single corner ; 
you will see the book printed in more places and lan- 
guages than one ; and just for this reason, I wish they 
would prohibit all good books. My disgust arises from 
seeing myself deprived of w^hat I most desire of this 
sort, I mean your other dialogues ; and if, from this 
cause, I fail in having the pleasure of seeing them, I 
shall devote to a hundred thousand devils these unnatui'al 
and godless hypocrites." 

At the same time, Thomas Campanella, a monk, who 
had already distinguished himself by an apology for Gali- 
leo, (published in 1622), wrote to him from Rome :— 
''I learn with the greatest disgust, diat a congregation of 
angry theologians is forming to condemn your Dialogues, 
and that no single member of it has any knowledge of 


mathematics, or familiarity with ab^use speculations. I 
should advise you to procure a request from the Grand 
Duke that, among the Dominicans and Jesuits and The- 
atins. and secular priests whom they ai'e putting on this 
congregation against yom^ book, they should admit also 
Castelli and m.yself. " It appears, from subsequent letters 
both from Campanella and Castelh, that the required let- 
ter was procured and sent to Rome, but it was not thought 
prudent to irritate the opposite party by a request which 
it was then clearly seen would have been made in vain. 
Not only were these friends of Galileo not admitted to 
the congregation, but, upon some pretext, Castelli was 
even sent away from Rome, as if Galileo's enemies de- 
sired to have as few enlightened witnesses as possible of 
their proceedings ; and on the contrary, Scipio Chiara- 
monte, who had been long known for one of the staunch- 
€st and most bigoted defenders of the old system, and 
who, as Montucla says, seems to have spent a long life in 
nothing but retarding, as far as he was able, the progress 
of discover}^, was summoned from Pisa to complete their ■ 
number. From tliis period we have a tolerably continu- 
ous account of the proceedings against Galileo in the 
dispatches which Nicolini sent regularly to his court. It 
appears from them that Nicolini had several interviews 
with the Pope, whom he found highly incensed against 
Galileo, and in one of the earliest he received ,an inti- 
mation to advise the Duke ^'not to engage himself in this 
matter as he had done in the other business of Alidosi, 
because he would not ge^t tlarough it with honor.'- Find- 
ing Urban in this humor, N icolini thought it best to tem- 
I porize, and to avoid the appearance of any thing like 


direct opposition. On the 15lh of September, proba- 
bly as soon as the first report on Galileo's book had been 
made, Nicolini received a private notice from the Pope, 
^' in especial token of the esteem in which he held the 
Grand Duke," that he was unable to do less than con- 
sign the work to the consideration of the Inquisition. 
Nicolini was permitted to communicate this to the Grand 
Duke only, and both were declared Mable to ''the usual 
censures" of the Inquisition in case of divulging the 

The next step was to summon Galileo to Rome, and 
the only answer returned to all Nicolini 's representations 
of his advanced age of seventy years, the very infirm 
state of his health, and the discomforts which he must 
necessarily suffer in such a journey, and in keeping quar- 
antine, was that he might come at leisure and that the ' 
quarantine should be relaxed as much as pos&ible in his ! 
favor, but that it was indispensably necessary that he 
should be personally examined before the Inquisition at 
Rome. Accordingly, on the 13th of February, 1633, 
Nicolini announces Galileo's arrival, and that he had 
officially notified his presence to the Assessor and Com- 
missary of the Holy Office. Cardinal Barberino, Ur- 
ban's nephew, who seems on the w^hole to have acted a 
friendly part towards Galileo, intimated to him that his 
most prudent course would be to keep himself as much ! 
at home and as quiet as possible, and to refuse to see ' 
any but his most intimate friends. With this advice, ^ 
which was repeated to Mm from several quartos, Galileo J 
thought it best to comply, and kept himself entirely se- ^ 
eluded in Nicolini's palace, where he was as usual main-T i 


tained at the expense of the Grand Doke. Nelli quotes 
two letters, which passed between Ferdinand's minister 
Cioh and Nicolini, in which the former intimated that 
Galileo's expenses were to be defrayed only during the 
first month of his residence at Rome. Nicolini retm^n- 
ed a spirited answer, that in that case, after the time 
specified, he should continue to treat him as before at 
his own private cost. 

The permission to reside at the ambassador's palace 
whilst his cause was pending, was granted and received 
as an extraordinary indulgence on the part of the Inqui- 
sition, and indeed if we estimate the proceedings through- 
out against Galileo by the usual practice of that detesta- 
ble tribunal, it will appear that he was treated wdth un- 
usual consideration. Even when it became necessar}^ in 
the course of the inquiry to examine liim in person^ 
which was in the beginning of April, although his remov- 
al to the Holy Office was then insisted upon, yet he was 
not committed to close or strictly solitary confinement. 
On the contrary, he was honorably lodged in the apart- 
ments of the Fiscal of the Inquisition, where he was al- 
lowed the attendance of his own servant, w^ho was also 
permitted to sleep in an adjoining room, and to come 
and go at pleasure. His table was still furnished by Ni- 
colini. But, notw^ithstandina; the distinction with which 
he was thus treated, Galileo was annoyed and uneasy at 
being (though httle more than nominally) within the 
I walls of the Inquisition, He became exceedingly anx- 
i ious that the matter should be brought to a conclusion, 
; and a severe attack of his constitutional complaints ren- 
j dered him still more fretful and impatient. On the last 


day of April, about ten days after his first examination, 
he was unexpectedly permitted to return to Nicolini's 
house, although the proceedings were yet far from being 
brought to a conclusion. Nicolini attributes this favor 
to Cardinal Barberino, who, he says, liberated Galileo 
on his own responsibility, in consideration of the en- 
feebled state of his health. 

In the society of Nicolini and his family, Galileo re- 
covered something of his courage and ordinary cheerful- 
ness, although his return appears to have been permitted 
on express condition of a strict seclusion ; for at the 
latter end of May, Nicolini was obliged to apply for per- 
mission that Galileo should take that exercise in the ^^ 
open air which was necessary for his health ; on which. \ 
occasion he was permitted to go into the public gardens ' 
in a half-closed carriage. 

On the evening of the 20th of June, rather more than 
foul* months after Galileo's arrival in Rome, he was again 
summoned to the Holy Office, whither he went the fol- ' 
i lowing morning ; he was detained there during the whole I 
of that d|iy, and on the next day was conducted in a ' 
peniten^al dress^ to the Convent of Minerva, where the ^ 
Cardindls and Prelates, his judges, were assembled for - 
the purpose of passing judgment upon him, by which \ 
this venerable old man was solemnly called upon to re- ^ 
nounce and abjure, as impious and heretical, the opinions ' 
which his whole existence had been consecrated to form \ 
and strengthen. As we are not aware that this remark- -\ 
. , -J 

* S* irrito il Papa, e lo fece abjurare, comparendo il pover uomo con uno I 
straccio di camicia indosso, che faceva compassione, MS. nella Bibl. Mag-^ 
liab. Ventiiri. 


able record of intolerance and bigoted folly has ever 
been printed entire in English, we subjoin a hteral trans- 
lation of the whole sentence and abjuration. 

The Sentence of the Inquisition on Galileo. 

We, the undersigned, by the Grace of God, Cardi- 
nals of the Holy Roman Church, Inquisitors General 
throughout the whole Christian Republic,' Special Depu- 
ties of the Holy ApostoHcal Chair against heretical de- 

'^ Whereas you, Galileo, son of the late Vincenzo 
Galilei, of Florence, aged seventy years, were denoun- 
ced in 1615 to this Holy^ Office, for holding as true a 
false doctrine taught by many, namely, that the sun is 
immovable in the centre of the world, and that the earth 
moves, and also with a diurnal motion; also, for having 
pupils whom you instructed in the same opinions; also, 
for maintaining a correspondence on the same with some 
German mathematicians ; also, for publishing certain 
letters on the solar spots, in which you developed the 
same doctrines^as true ; also, for answering the objec- 
tions which were continually produced from the Holy 
Scriptures, by glozing the said Scriptures according to 
j your own meaning; and whereas thereupon was produ- 
ced the cop3^ of a writing, in form of a letter professedly 
,, written by you to a person formerly your pupil, in 
1 which, following the hypotheses of Copernicus, you in- 
ii dude several propositions contrary to the true sense and 
authority of the Holy Scripture: therefore this holy tri-^ 
ibunal being desirous of providing against the disorder 
jand mischief which was thence proceeding and increas- 


ing to the detriment of the holy faith, by the desire of 
his Hohness, and of the Most Eminent Lords Cardmals 
of this supreme and universal Inquisition, the two prop- 
ositions of the stability of the sun, and motion of the 
earth, were qualified by the Theological Qualifiers as 

') ^'Ist, The proposition that the Sun is in the centre of 
I the world and immovable from its place ^ is absurd^ phi- 
\ losophically false^ and formally heretical ; because it is 
Uxpressl}^ contrary to the Holy Scripiurer 

2dly, The proposition that the Earth is not the centre 

of the world^ nor immovable^ but that it moves^ and also 

with a diurnal motion^ is also absurd^ philosophically 

tfalse^ aml^ theologically considered^ at least erroneous 

in faith. 

" But whereas being pleased at that time to deal mild- 
ly wuth you, it was decreed in the holy Congregation, 
held before His Hohness on the 25th day of Februaiy, 
1616, that His Eminence the Lord Cardinal Bellarmine 
should enjoin you to give up altogether the said false 
doctrine; if you should refuse, that you should be order- 
ed by the Commissary of the Holy Office to relinquish 
it, not to teach it to others, nor to defend it, nor ever 
i mention it, and in default of acquiescence that you 
, should be imprisoned; and in execution of this decree, 
on the following day at the palace, in the presence of 
His Eminence the said Lord Cardinal Bellarmine, after 
you had been mildly admonished by the said Lord Car- 
dinal, you were commanded by the acting Commissary 
of the Holy Office, before a notary and witnesses, to 
relinquish altogether the said false opinion, and in future 


neither to defend nor teach it in any manner, neither 
verbally nor in writing, and upon your promising obedi- 
ence you were dismissed. 

'^ And in order that so pernicious a doctrine might be 
altogether rooted out, nor insinuate itself farther to the 
heavy detriment of the Catholic truth, a decree emana- 
ted from the Holy Congregation of the Index* prohibit- 
ing the books which treat of this doctrine ; and it was 
declared false, and altogether contrary to the Holy and 
Divine Scripture. 

''And whereas a book has since appeared, pubhshed 
at Florence last year, the title of which showed that 
you were the author, which title is: The Dialogue of 
Galileo Galilei^ on the two principal systems of the 
worlds the Ptolemaic and Copernican; and whereas the 
Holy Congregation has heard that, in consequence of 
the printing of the said book, the false opinion of the 
earth's motion and stabihty of the sun is daily gaining 
ground; the said book has been taken into careful con- 
sideration, and in it has been detected a glaring violation 
of the said order, which had been intimated to you; in- 
asmuch as in this book you have defended the said opin- 
ion, aheady and in your presence condemned; although 

* The Index is a list of books, the reading of which is prohibited to Ro- 
Qiafl Catholics, This list, in the early periods of the Reformation, was often 
consulted by the curious, who were enlarging their libraries ; and a storj' is 
curreet in England, that, to prevent this mischief, the Index itself was inserted 
in its own forbidden catalogue. The origin of this story is, that an index 
was published in Spain, particularizing the objectionable passages in such 
books as were only partially condemned; and although compiled with the 
best intentions, this was found to be so racy, that it became necessary to 
forbid the circulation of this edition in aibsequent lists. 



in the said book you labor with many circumlocutions 
to induce the behef that it is left by you undecided, and 
in express terms probable: which is equally a very 
grave error, since an opinion can in no way be probable 
which has been already declared and finally determined 
contrary to the divine Scripture. Therefore by Our 
order you have been cited to this Holy Office, where, | 
on your examination upon oath, you have acknowledged 
the said book as written and printed by you. You also 
confessed that you began to write the said book ten or 
twelve years ago, after the order aforesaid had been 
given. Also, that you demanded Hcense to publish it, 
but without signifying to those who granted you this per- 
mission that you had been commanded not to hold, de- 
fend, or teach the said doctrine in any manner. You 
also confessed that the style of the said book was, in 
many places, so composed that the reader might think 
the arguments adduced on the false side to be so worded 
as more effectually to entangle the understanding than 
to be easily solved, alleging in excuse, that you have 
thus run into an error, foreign (as you say) to your in- 
tention, from writing in the form of a dialogue, and in 
consequence of the natural complacency which every 
one feels with regard to his own subtilties, and in show- 
ing himself more skillful than the generality of mankind 
in contriving, even in favor of false propositions, ingen- 
ious and apparently probable arguments. 

'' And, upon a convenient time being given to you for 
making your defense, you produced a certificate in the 
hand-writing of His Eminence the Lord Cardinal Bellar- 
mine, procured, as you said, by /ourself, that you might 
defend yourself against the calumnies of your enemies^ . 


who reported that you had abjured yom^ opinions, and 
had been punished by the Holy Office ; in which certifi- 
cate it is declared, that you had not abjured nor had 
been punished, but merely that the declaration made by 
His Holiness, and promulgated by the Holy Congrega- 
tion of the Index, had been announced to you, which 
declares that the opinion of the motion of the earth, and 
stability of the sun, is contrary to the Holy Scriptures, 
and, therefore, cannot be held or defended. Wherefore 
since no mention is there made of two articles of the or- 
der, to wit, the order 'not to teach,' and 'in any man- 
ner ' you argued that we ought to believe, that in the 
lapse of fourteen or sixteen years, they had escaped your 
memory, and that this was also the reason why you were 
silent as to^the order, when you sought permission to pub- 
lish your book, and that this is said by you not to excuse 
your error, but that it may be attiibuted to vain-glorious 
ambition, rather than to malice. But tliis very certifi- 
cate, produced on your behalf, has greatly aggravated your 
offense, since it is therein declared that the said opinion is 
contrary to the Holy Scripture, and yet you have dared 
to treat of it, to defend it, and to argue that it is prob- 
able ; nor is there any extenuation in the license art- 
fully and cunningly existed by you, since you did not 
intimate the command imposed upon you. . But where- 
as it appeared to Us that you had not disclosed the whole 
truth with regard to your intentions, We thought it ne- 
cessary to proceed to the rigorous examination of you, 
in w^hich (without any prejudice toi: w^hat you had con- 
fessed, and which is above detailed agamst you, wdth re- 
gard to your said intention) you answered like a good 


'^ Therefore, having seen and maturely considered the 
merits of your cause, with your said confessions and e^:- 
cuses, and every thing else which ought to be seen and 
considered. We have come to the underwTitten final sen- 
tence against you. 

'^ Invoking, therefore, the most holy name of Our 
Lord Jesus Christ, and of His Most Glorious Virgin 
Mother Mary, by this Om^ final sentence, which, sitting 
in coimcil and judgment for the tribunal of the Reverend 
Masters of Sacred Theology, and Doctors of both Laws, 
Our Assessors, We put forth in this writing touching the 
matters and controversies before L^s, between The Mag- 
nificent Charles Sincerus, Doctor of both Laws, Fiscal 
Proctor of this Holy Office of the one part, and you^ 
Galileo Galilei, an examined and confessed criminal fi'om 
this present \ratmg now in progress as above of the oth- 
er part,^? We pronounce, judge, and declai'e, that you, 
the said Galileo, by reason of these tilings which have 
been detailed in the course of this writing, and which, 
as above, you have confessed, have rendered yourself 
vehemently suspected by this Holy Ofiice of heresy: 
that is to say, that you beUeve and hold tlie false doc- 
trine, and contrary to the Holy and Divine Scriptures, 
namely, that the sun is the centre of the world, and that 
it does not move from east to west, and that the earth 
does move, and is not the centre of the world ; also that 
an opinion can be held and supported as probable, after 
it has been declared and finally decreed contrary to the 
Holy Scripture, and consequently that you have incurred 
all the censures and penalties enjoined and promulgated 
in the sacred canons, and other general and particular 


constitutions against delinquents of this description. 
From which it is Our pleasure that you be absolved, 
provided that, first, with a sincere heart and unfeigned 
faith, in Our presence, you abjure, curse, and detest the 
said errors and heresies, and every other error and here- 
sy contrary to the Catholic and Apostohc Church of 
Rome in the form now sho\\Ti to you. 

^'But, that your grievous and pernicious error and 
transgression may not go altogether unpunished, and that 
you may be made more cautious in future, and may be a 
warning to others to abstain from delinquencies of this 
sort, We decree that the book of the dialogues of Galileo 
Galilei, be prohibited by a pubhc edict, and We con- 
demn you to the formal prison of this Holy Office for a 
period determinable at Our pleasure ; and, by way of 
salutary penance. We order you, during the next three 
years, to recite once a week the seven penitential psalms, 
reserving to Ourselves the power of moderating, com- 
muting, or taking off the whole or part of the said pun- 
ishment and penance. 

''And so We say, pronounce, and by Our sentence de- 
clare, decree, and reserve, in this and in every other bet- 
ter form and manner, which la\\^ully We may and can use. 
^' So We, the subscribing Cardinals pronounce. 
Felix, Cardinal di Ascoli, 
Guido, Cardinal Bentivogho, 
Desiderio, Cardinal di Cremona, 
Antonio, Cardinal S. Onofrio, 
Berlingero, Cardinal Gessi, 
Fabricio, Cardinal Verospi, 
Martino, Cardinal Ginetti.'^ 


We cannot suppose that Galileo, even broken down as 
he was with age and infirmities, and overawed by the 
merciless tribunal to whose power he was subjected, 
could without extreme reluctance thus formally give the 
lie to his whole life, and call upon God to witness his 
renunciation of the opinions which even his bigoted judg- 
es must have felt that he still clung to in his heart. 

We know^ indeed that his friends w^ere unanimous in 
recommending an unqualified acquiescence in whatever 
might be required, but some persons have not been able 
to find an adequate explanation of his submission, either 
in their exhortations, or in the mere dread of the alterna- ^\ 
tive which might await him in case of non-compliance. 
It has in short been supposed, although the suspicion 
scarcely rests upon grounds sufficiently strong to ^varr^t 
the assertion, that Galileo did not submit to this ajajura- j 
tion until forced to it, not merely by the apprehension, ! 
but by actual experience of personal violence. The ar- ] 
guments on wliich this horrible idea appears to be main- 
ly founded are the two following : First, the Inquisitors 1 
declare in their sentence that, not satisfied with Galileo's i 
first confession, they judged it necessaiy to proceed '' to i 
tlie rigorous examination of him, in which he answered i 
like a good Catholic.^ It is pretended by those who are 
more familiar wdth inquisitorial language than we can pro- ; 
fess to be, that the words il rigorosa esame^ form the , 
official phrase for tlie application of the torture, and ac- ! 
cordingly they interpret this passage to mean, that the ! 
desired answers and submission had thus been extorted 

' *Giudicassimo esser necessario venir contro di te al rigoroso esame nel 
quale rispondesti cattolicaraente. i 


from Galileo, which his judges had otherwise failed to 
get from him. And, secondly, the partisans of this opin- 
ion bring forward in corroboration of it, that Galileo im- 
mediately on his departure from Rome, in addition to his 
old complaints, was found to be afflicted with hornia, 
and this was a common consequence of the torture of the 
cord, which they suppose to have been inflicted. It is 
right to mention that no other trace can be found of this 
supposed torturing in all the documents relative to the 
proceedings against Gahleo, at least Venturi was so 
assured by one who had inspected the originals at Paris. "^ 
Although the arguments we have mentioned appear 
to us slight, yet neither can we attach much importance 
to the contrast which the favorers of the opposite opinion 
profess to consider so incredible between the honorable 
manner in which Galileo was treated throughout the rest 
of the inquiry, and the suspected harsh proceeding against 
him. Whether Galileo should be lodged in a prison or 
a palace, was a matter of far other importance to the In- 
quisitors and to their hold upon public opinion, than the 
question w^hether or not he should be suffered to exhibit a 
persevering resistance to the censures which they were 
prepared to cast upon him. Nor need w^e shrink from 

*Thefateof these documents is curious; after being long preserved at 
Rome, they were carried away in 1809, by order of Buonaparte, to Paris, 
where they remained till his first abdication. Just before Jthe hundred days, 
the late king of France, wishing to inspect them, ordered that they should l)e 
brought to his own apartments for that purpose. In the hasty flight which 
aoon afterwards followed, the manuscripts were forgotten, and it is not known 
what became of them. A French translation, begun by Napoleon's desire, 
I was completed only down to the 30th of April, 1633, the date of Galileo'a 
first return to Nicol in i's palace. 


the idea, as we might from suspecting of some gross 
crime, on trivial grounds, one of hitherto unblemished 
innocence and character. The question may be disen- 
cumbered of all such scruples, since one atrocity more 
or less can do little towards affecting our judgment of 
the unholy Office of the Inquisition. 

Delambre, who could find so much to reprehend in 
Galileo's former uncompromising boldness, is deeply 
penetrated with the insincerity of his behavior on the 
present occasion. He seems to have forgotten that a 
tribunal which finds it convenient to carry on its inquiries 
in secret, is always hable to the suspicion of putting 
words into the mouth of its victims ; and if it were worth 
while, there is sufficient internal evidence that the lan- 
guage which Galileo is made to hold in his defense and 
confession, is rather to be read as the composition of his 
judges than his own. For instance, in one of the letters 
which we have extracted, it may be seen that this obnox- 
ious work was already in forward preparation as early as 
1610, and yet he is made to confess, and the circum- 
stance appears to be brought forward in aggravation of 
his guilt, that he began to write it after the prohibition 
which he had received in 1616. 

The abjuration was drawn up in the following 
terms : — 

The abjuration of Galileo. 

" I Galileo Galilei, son of the late Vincenzo Galilei, 
k)f Florence, aged 70 years, being brought personally to 
judgment, and kneeling before you, Most Eminent and 
Most Reverend Lords Cardinals, General Inquisitors of 



the universal Christian republic against heretical depravi- 
ty, having before my eyes the Holy Gospels, which I 
touch with my own hands, swear, that I have always be- 
lieved, and now believe, and with the help of God will 
in future believe, every article which the Holy Catholic 
and Apostohc Church of Rome holds, teaches, and preach- 
es. But because I had been enjoined by this Holy 
Office altogether to abandon the false opinion which main- 
tains that the sun is the centre and immovable, and for- 
bidden to hold, defend, or teach, the said false doctrine 
in any manner, and after it had been signified to me that 
the said doctrine is repugnant with the Holy Scripture, 
I have written and printed a book, in which I treat of the 
same doctrine now condemned, and adduce reasons with 
great force in support of the same, without giving any 
solution, and therefore have been judged grievously sus- 
pected of heresy ; that is to say, that 1 held and believed 
that the sun is the centre of the world and immovable^ 
and that the earth is not the centre and movable, Will-^ 
ing, therefore, to remove from the minds of Your Emi^ 
nences, and of every Catholic Christian, this vehement 
suspicion rightfully entertained towards me, with a sincere 
heart and unfeigned faith, I abjure, curse, and dete&t the 
said errors and heresies, and generally every other error 
and sect contrary to the said Holy Church ; and I swear^ 
that I will never more in future say or assert anything 
verbally, or in writing, which may give rise to a similar 
suspicion of me: but if I shall know any heretic, or any 
one suspected of heresy, that I will denounce him to this 
Holy Office, or to the Inquisitor and Ordinary of the 
place in which I may be. I swear, moreover, and 


promise, that I will fulfil, and observe fully, all the pen-| 
aiices which have been, or shall be laid on me by this I 
Holy Office. But if it shall happen that I violate any of j 
my said promises, oaths, and protestations, (which God, 
avert!) I subject myself to all the pains and punishments i 
which have been decreed and promulgated by the sacred \ 
canons, and other general and particular constitutions, 
against delinquents of this description. So may Grod! 
help me, and his Holy Gospels, which I touch with my 
own hands. I, the above-named Galileo Galilei^ havei 
abjured, svi^orn, promised and bound myself, as above, 
and in witness thereof with my own hand have subscri- 
bed this present writing of my abjuration, which I have 
recited word for word. At Rome in the Convent ot 
Minerva, 22d June, 1633, I, Galileo Galilei, have ab-! 
jured as above with my own hand." i 

It is said that Galileo, as he rose from his knees,! 
stamped on the ground, and whispered to one of hisj 
friends, E pur si muove — (It does move though.) \ 

Copies of Galiieo's sentence and abjuration were im~^ 
mediately pronjiflgated in every direction and the profes«| 
sors at several universities received directions to read 
them publicly. At Florence this ceremony took place 
in the church of Sta. Croce, whither Guiducci, Aggiun- 
ti and all others who were known in that city as firm ad- ] 
herents to Galileo's opinions, were specially summoned. ' 
The triumph of the '' Paper Philosophers" was so far. 
complete, and the alarm occasioned by this proof of their 
dying power extended even beyond Italy. ^'I have j 
been told," writes Descartes from Holland to Mersenne I 
Paris, ''that Galileo 's system was printed in Italy last year, j 


but that every copy has been burnt at Rome, and himself 
condenmed to some sort of penance, which has astonish- 
ed me so much that I have almost determined to bui^n all 
my papers, or at least never to let them be seen by any 
one. I cannot collect that he, who is an Itahan and 
even a freind of the Pope, as I understand, has been crim- 
inated on any other account than for having attempted 
to establish the motion of the earth. I know that this 
opinion was formerly censured by some Cardinals, but I 
thought I had since heard, that no objection was now 
made to its being publicly taught, even at Rome." 

The sentiments of all who felt themselves secured 

against the apprehension of personal danger could take 

but one direction, for, as Pascal well expressed it in one 

of liis celebrated letters to the Jesuits^ — ''It is in vain 

that you have procured against Galileo a decree from 

Rome condemning his opinion of the earth's motion. 

Assuredly, that will never prove it to be at rest ; and if 

we have unerring observations proving that it turns round, 

not all mankind together can keep it from turning, nor 

themselves from turning with it." 

The assembly of doctors of the Sorbonne at Paris nar- 

I rowly escaped from passing a similar sentence upon the 

1 system of Copernicus. The question was laid before them 

by Richeheu, and it appears that their opinion was for a 

moment in favor of confirming the Roman decree. It is 

\ to be wished that the name had been preserved of one 

\ of its members, who, by his strong and philosophical 

representations, saved that celebrated body from this 



Those who saw nothing in the punishment of Galileo 
but passion and blinded superstition, took occasion to 
revert to the history of a similar blunder of the Court of 
Rome in the middle of the eighth century. A Bavarian 
bishop named Virgil, eminent both as a man of letters 
' and politician, had asserted the existence of Antipodes, 
which excited in the ignorant bigots of his time no less 
alarm than did the motion of the earth in the seventeenth 
century. Pope Zachary, who was scandalized at the idea 
of another earth inhabited by another race of men, and 
enlightened by another sun and moon, (for this was the 
shape which Virgil's system assumed in his eyes) sent out 
positive orders to his legate in Bavaria. '' With regard 
to Virgil, the philosopher, (I know not whetlier to call 
him priest,) if he own these perverse opinions, strip him 
of his preisthood, and drive him from the church and al- 
ters of God. " But Virgil had himself occasionally acted 
as legate, and was moreover too necessary to his sover- 
eign to be easily displaced. He utterly disregarded 
these denunciations, and during twentj^-five years, which 
elapsed before his death, retained his opinions, his bish- 
oprick of Salzburg, and his political power. He was 
afterwards can^fiized. 

Even the most zealous advocates of the authority of 
Rome were embarrassed in endeavoring to justify the 
treatment which Galileo experienced. Tiraboschi has 
attempted to draw a somewhat subtle distinction between 
the bulls of the Pope and the inquisitorial decrees which 
were sanctioned and approved by him ; he dwells on the 
reflection that no one, even among the most zealous 
Catholics, has ever claimed infallibiUty as an attribute of 


the Inquisition, and looks upon it as a special mark of 
grace accorded to the Roman CathoHc Church, that during 
the whole period in which most theologians rejected the 
opinions of Copernicus, as contrary to the Scriptures the 
head of that Church was never permitted to compromise 
his infallible character by formally condemning it.^ 

Whatever may be the value of this consolation, it can 
hardly be conceded, unless it be at the same time admit- 
ted that many scrupulous members of the Church of 
Rome have been suffered to remain in singular misappre- 
hension of the nature and sanction of the authority to 
which Galileo had yielded. The words of the bull of 
Sixtus v., by which the Congregation of the Index v>'as 
remodeled in 1588, are quoted by a professor of the 
University of Louvain, a zealous antagonist of Galileo as 
follows : '^ They ai'e to examine and expose the books 
which are repugnant to the CathoHc doctrines and Chris- 
tian discipline, and after reporting on them to us they are 
to condemn them by our authority.'' Nor does it ap- 
pear that the learned editors of what is commonly called 
I the Jesuit's edition of Newton's '' Principia" were of 
; opinion, that in adopting the Copernican system they 
I should transgress a mandate emanating from any thing 
t short of infallible wisdom. The remarkable words which 

* La Chiesa non ha mai dichiarati eretici i sostenitori del Sisteraa Co- 
pernicanoj e questa troppo rigorosa ceasura non usci che dal tribunale della 
Romana Inqiiisizione a cui niuno tra Cattolici ancor piu zelanti ha mai at- 
jtribuito il diritto dell' infallibilita. Anzi in cio ancora e d' ammirarsi la 
.providenza di Dio a favor della Chiesa, percioche iu un tempo in cui la 
maggior parte dei teologi fermamente credavano che il Sistema Copernicano 
ftosse all' autorita delle sacre Carte contrario, pur non permise che dalla 
IChiesa si proferisse su cio un solenne giudizio. — Stor. della Lett. Ital. 


they were compelled to prefix to their book, show how 
sensitive the court of Rome remained, even so late as 
1742, with regard to this rashly condemned theory. In 
their preface they say: "Newton in this third book 
supposes the motion of the earth. We could not ex- 
plain the author's propositions otherwise than by making 
the same supposition. We are therefore forced to sus- 
tain a character which is not our own; but we profess to 
pay the obsequious reverence which is due to the de- 
crees pronounced by the supreme Pontifis against the 
motion of the earth." 

This coy reluctance to admit what nobody any longer 
doubts has survived to the present time ; for BaiUi in- 
forms us, that the utmost endeavors of Lalande, when 
at Rome, to obtain that Galileo^s work should be erased 
from the Index, were entirely ineffectual, in consequence 
of the decree which had been fulminated against liim ; 
and in fact, both it and the book of Copernicus, '^ Nisi 
Corrigatur," are still to be seen on the forbidden hst 
■ of 1828. 

The condemnation of Galileo and his book was not 
thought sufficient. Urban's indignation also vented it- 
self upon those who had been instrumental in obtaining 
the license for him. The inquisitor at Florence was 
reprimanded ; Riccardi, the master of the sacred palace, 
and Ciampoli, Urban's secretary, were both dismissed 
from their situations. Their punislinient appeal's rathei 
anomalous and inconsistent with the proceedmgs agains 
Gahleo, in which it was assumed that his book was no 
properly licensed ; yet the others suffered on account o 
granting that very hcense, w4iich he was accused of hav 



ing surreptitiously obtained from them, by concealing 
circumstances with which they were not? bound to be oth- 
erwise acquainted. Riccardi, in exciflpation of his con- 
duct, produced a letter in the hand-writing of Ciampoli, 
in which *was contained that His Holiness, in whose 
presence the letter professed to be \mtten, ordered the 
license to be given. Urban only rephed that this was a 
Ciampolism ; that his secretaiy and Gahleo had circum- 
vented him : that he had already dismissed Ciampoh, 
and that Riccardi must prepare to follow him. 

As soon as the ceremony of abjuration was concluded, 
Galileo was consigned, pui'suant to his sentence, to the 
prison of the Inquisition. Probably it was never intend- 
ed that he should long remain there, for at the end of 
foui^ days, he was reconducted on a very slight represen- 
tation of Nicolini to the ambassador's palace, there to 
await his fuilher destination. Florence was still suffer- 
ing under the before-mentioned contagion; and Sienna 
was at last fixed on as the place of his relegation. He 
would have been shut up in some convent in that city, if 
Nicolini had not recommended as a more suitable re- 
sidence, the palace of the Archbishop Piccolomini, 
whom he knew to be among Galileo's warmest friends. 
Urban consented to the change, and Galileo finally left 
Rome for Si^lma in the early part of July. , 

Piccolommi received him with the utmost kindness, 
controlled of course by the strict injunctions which were 
dispatched from Rome, not to suffer him on any account 
to quit the confines of the palace. Galileo continued at 
Sienna in this state of seclusion till December of the 
same year, when the contagion having ceased in Ti^ca- 


ny, he^pplied for permission to return to his villa at 
Aro^ri. This was allowed, subject to the same restric- 
tions under which he had been residing with the arch- 


Extracts from the Dialogues on the System. 

After narrating the treatment to which Galileo w^as 
subject on account of his admirable Dialogues, it wdll 
not be irrelevant to endeavor, by a few extracts, to con- 
vey some idea of the style in which they are written. 
It has been mentioned, that he is considered to surpass 
all other Itahan wTiters (unless we except Machiavelli) 
in the purity and beauty of his language, and indeed 
his principal followers, who avow^edly imitated his style, 
make a distinguished group among the classical authors 
of modern Italy. He professed to have formed himself 
from the study of Ariosto, whose poems he passionately 
admired, insomuch that he could repeat the greater part 
of them, as well as those of Berni and Petrarca, all 
which he was in the frequent habit of quoting in conver- 
sation. The fashion and almost universal practice of 
that day was to write on philosophical subjects in Latin ; 
and although Galileo wrote very passably in that lan- 
guage, yet he generally perferred the use of Italian, for 


which he gave his reasons in the following characteristic 
manner : — 

" I wrote in Italian because I wished every one to 
be able to read what I wrote ; and for the same cause I 
have written my last treatise in the same language : the 
reason which has induced me is, that I see young men 
brought together indiscriminately to study to become 
physicians, philosophers, &c., and whilst many apply 
to such professions who are most unfit for them, others 
who would be competent remain occupied either with 
domestic business, or with other employments alien to 
literature ; who, although furnished, as Ruzzante might 
say, with a decent set of brains^ yet, not being able to 
understand things written in gibberish^ take it into their 
heads, that in these crabbed fol^d's there must be some 
grand hocus pocus of logic and philosophy much too high 
up for them to think of jumping at. I want them to 
know, that as Nature has given eyes to them, just as well 
as to philosophers, for the purpose of seeing her works, 
she has also given them brains for examining and un- 
derstanding them." 

The general structure of the Dialogues has been 
already described ; we shall therefore premise no more 
ithan the judgment pronounced on them by a highly 
'gifted writer, to supply the deficiencies of our necessari- 
ly imperfect analysis. 

'' One forms a very imperfect idea of Galileo, from 
'considering the discoveries and inventions, numerous 
land splendid as they are, of which he was the undis- 
puted author. It is by following his reasonings, and by 
|pur suing the train of his thoughts, in his own elegant, 


though somewhat diffuse exposition of them, that we 
become acquainted with the fertihty of his genius — 
with the sagacity, penetration, and comprehensiveness 
of his mind. The service which he rendered to real 
knowledge is to be estimated, not only from the truths 
which he discovered, but from the errors which he 
detected — not merely from the sound principles which 
he estabhshed, but from the pernicious idols which he 
overtlirew. The Dialogues on the System are written 
with such singular felicity, that one reads them at the 
present day, when the truths contained in them are 
known and admitted, with all the dehght of novelty, 
and feels one's self carried back to the period when the 
telescope was first directed to the heavens, and when 
the earth's motion, with all its train of consequences, 
was proved for the first time." 

The first dialogue is opened by an attack upon the 
arguments by which Aristotle pretended to determine 
a priori the necessary motions belonging to different 
parts of the world, and on his favorite principle, that 
particular motions belong naturally to particular sub- 
stances. Salviati (representing Galileo) then objects 
to the Aristotelian distinctions between the corruptible 
elements and incorruptible skies, instancing among 
other things the solar spots and newly appearing stars, as 
arguments that the other heavenly bodies may probably 
be subjected to changes similai' to those which are con- 
tinually occurring on the earth, and that it is the great 
distance alone which prevents their being observed. 
After a long discussion on this point, Sagredo exclaims, 
'' I see into the heart of Simphcio, and perceive that he 


is much moved by the force of these too conclusive ar- 
guments ; but metliinks I hear him say — ' Oh, to 
whom must we betake ourselves to settle our disputes, if 
Aristotle be removed from the chair? What other 
author have we to follow in our schools, our studies, 
and academies? What philosopher has written on all 
the parts of Natural Philosophy, and so methodically as 
not to have overlooked a single conclusion ? Must we 
then desolate this fabric, by which so many travelers 
have been sheltered ? Must we destroy this asylum, 
this Prytaneum wherein so many students have found a 
convenient resting-place, where, without being exposed 
to the injuries of the weather, one may acquire an 
intimate knowledge of nature, merely by turning over a 
few leaves? Shall we level this bulwark, behind which 
we are safe from every hostile attack? ' I pity him no 
less than I do one who at great expense of time and 
treasure, and with the labor of hundreds, has built up a 
very noble palace ; and then, because of insecure foun- 
dations, sees it ready to fall — unable to bear that those 
walls be stripped that are adorned with so many beauti- 
ful pictures, or to suffer those columns to fall that uphold 
the stately galleries, or to see ruined the gilded roofs, 
the chimney-pieces, the friezes, and marble cosfiiices 
erected at so much cost, he goes about it with^ girders 
and props, with shores and buttresses, to hinder its 

Salviati proceeds to point out the many points of 
similarity between the earth and moon, and among 
others which we have already mentioned, the fcUowing 
rem-ai'k deserves especial notice : — 


'^ Just as from the mutual and universal tendency of 
the parts of the earth to form a whole, it follows that 
they all meet together with equal inchnation, and that 
they may unite as closely as possible, assume the 
spherical form ; why^ought we not to believe that the 
moon, the sun, and other mundane bodies are also of a 
round figure, from no other reason than from a common 
instinct and natural concourse of all their component 
parts ; of which if by accident any one should be 
violently separated from its whole. It is not reasonable to 
beheve that spontaneously, and of its natural instinct, it 
would return? It may be added, that if any centre of 
the universe may be assigned to which the whole 
terrene .globe if thence removed would seek to return, 
we shall find most probable that the sun is placed in it, 
as by the sequel you shall understand." 

Many who are but superficially acquainted with the 
History of Astronomy, are apt to suppose that Newton's 
great merit was in his being the first to suppose an at- 
tractive force existing in and between the different bod- 
ies composing the solar system. This idea is very er- 
roneous ; Newton's discovery consisted in conceiving 
and proving the identity of the force with which a stone 
falls, and that by which the moon falls, towards the 
earth (on an assumption that this force becomes weaker in 
a certain proportion as the distance increases at which it 
operates), and in generalizing this idea, in applying it 
to all the visible creation, and tracing the principle of 
universal gravitation with the assistance of a most re- 
fined and beautiful geometry into many of its most re- 
mote consequences. But the general notion of an 


attractive force between the sun, moon, and planets, was 
very commonly entertained before Newton was born, 
and may be traced back to Xepler, who was probably 
the first modern philosoper who suggested it. The 
following extraordinary passages from his ''Astronomy" 
will show the nature of his conceptions on this sub- 
ject :— 

" The true doctrine of gravity is founded on these 
axioms : every corporeal substance, so far forth as it is 
corporeal, has a natural fitness for resting in every 
place where it may be situated by itself beyond the 
sphere of influence of its cognate body. Gravity is a 
mutual affection between co^j;a:ate bodies towai'ds union 
or conjunction, (similar in kind to the magnetic virtue), 
so that the earth attracts a stone much rather than the 
stone seeks the earth. Heavy bodies (if in the first 
place we put the earth in the centre of the w^orld) are 
not carried to the centre of the world in its quality of 
centre of the world, but as to the centre of a cognate 
round body, namely the earth. So that wheresoever 
the earth may be placed, or withersoever it may be 
carried by its animal faculty, heavy bodies w411 always 
be carried towards it. If the earth were not round, 
heavy bodies would not tend from every side in a straight 
line towards the centre of the earth, but to different 
points from different sides. If two stones were placed 
in any part of the world near each other, and beyond the 
sphere of influence of a third cognate body, these stones, 
like tw^o magnetic needles, would come together in the 
intermediate point, each approaching the other by a 
space proportional to the comparative mass of the other* 


If the moon and earth were not retained in their orbits I 
by their animal force or some other equivalent, the earth | 
would mount to the moon by a fifty-fourth part of their 
distance, and the moon fall toward the earth through the , 
other fifty -three parts, and would there meet, assuming | 
however that the substance of both is of the same density, i 
If the earth should cease to attract its waters to itself, all i 
the waters of the sea would be raised, and would flow to i 
the body of the moon." i 

He also conjectured that the irregularities in the moon's j 
motion were caused by the joint action of the sun and i 
earth, and recognized the mutual action of the sun and , 
planets, when he declared the mass and density of the j 
sun to be so great that the united attraction of the other j 
planets cannot remove it from its place. Among these J 
bold and brilliant ideas, his temperament led him to in- j 
troduce others which show how unsafe it was to follow j 
his guidance, and which account for, if they do notj 
altogether justify, the sarcastic remark of Ross, that| 
"Kepler's opinion that the planets are moved round by ij 
the sunne, and that this is done by sending forth a magnet- 
ic virtue, and that the sun-beames are like the teethe, of 
a wheele taking hold of the planets, are senslesse croU^liets 
fitter for a wheeler or a miller than a philosopher."* '■ 
Roberval took up Kepler's notions, especially in the ' 
tract which he falsely attributed to Aristarchus, and it is i 
much to be regretted that Roberval should deserve cred- \ 
it for anything connected with that impudent fraud. ' 
The principle of universal gravitation, though not the va- i 

* The new Planet no Planet, or the Earth no wandering Star, except in ^ 
the wandering heads of Galileans. London, 1646. 


rying proportion, is distinctly assumed in it, as the follow- 
ing passages will sufficiently prove: ''In every single 
particle of the earth, and the terrestrial elements, is a cer- 
tain property or accident which we sr.ppose common to 
the whole system of the world, by virtue cf which aJl its 
parts ai-3 forced together, and reciprocally attract each 
other ; and this property is found in a greater or less 
degree in the different particles, according to their densi- 
ty. If the earth be considered by itself, its centres of 
magnitude and virtue, or gravity, as we usually call it, 
will coincide, to which all its parts tend in a straight line 
as well by their own exertion or gravity, as by the recip- 
rocal attraction of all the rest." In a subsequent chap- 
ter, Roberval repeats these passages nearly in the same 
words, applying them to the whole solar system, adding, 
that " the force of this attraction is not to be considered 
as residing in the centre itself, as some ignorant people 
think, but in the w4iole system whose parts are equally 
disposed round the centre." This very curious work 
was reprinted in the thkd volume of the Reflexiones Phy- 
sico-MathematiccB of Mersenne, from whom RobeiTal 
pretended to have received the Arabic manuscript, and 
who is thus irretrievably impUcated in the forgery. The 
last remark, denying the attractive force to be due to any 
property of the central point, seems aimed at Aristotle, 
who, in a no less curious passage, maintaining exactly 
the opposite opinion, says, " Hence, we may better un- 
derstand what the ancients have related, that like things 
are wont to have a tendency to each other. For this is 
not absolutely true ; for if the earth were to be removed 
to the place now occupied by the moon, no part of the 


earth would then have a tendency towards that place, 
but would still fall towards the point which the earth's 
centre now occupies." Mersenne considered the con- 
sequences of the attpctive force of each particle of nriat- 
ter so far as to remark, that if a body were supposed to 
fall towards the centre of the earth, it would be retarded 
by the attraction of the part through which it had already 
fallen. Galileo had not altogether neglected to specu- 
late on such a supposition, as is plain from the following 
extract. It is taken from a letter to Carcaville, dated 
from Arcetri, in 1637. " I will say farther, that I have 
net absolutely and clearly satisfied myself that a heavy 
body would arrive sooner at the centre cf the earth, 
if it began to fall from the distance only of a sin- 
gle yard, than another which should start from the dis- 
tance of a thousand miles. I do not affirm tliis, but I 
offer it as a paradox." 

It is very difficult to offer any satisfactory comment 
upon this passage ; it may be sufficient to observe that 
this paradoxical result was afterwards deduced by New- 
toU) as one of the consequences of the general law v/ith 
which all nature is pervaded, but with which there is no 
reason to believe that Galileo had any acquaintance ; in- 
deed the idea is fully negatived by other passages in this 
same letter. This is one of the many instances from 
which we may learn to be cautious how we invest de- 
tached passages of the earlier mathematicians with a 
meaning which in many cases their authors did not con- 
template. The progressive development of these ideas 
in the hands of WalHs, Huyghens, Hook, Wren, and 
Nev/ton, would lead us too far from our principal sub- 


ject. There is another passage in the third Dialogue 
connected with this subject, which it may be as well to 
notice in this place. " The parts of the earth have such 
a propensity to its centre that when it changes its place, 
although they may be very distant from the globe at 
the time of the change, yet must they follow. An ex- 
ample similar to this is the perpetual sequence of the 
Medicean stars, although always separated from Jupiter. 
The same may be said of the moon, obhged to follow the 
earth. And this may serve for those simple ones who 
have difficulty in comprehending how these two globes, 
not being chained together, nor strung upon a pole, mutu- 
ally follow each other, so that on the acceleration or re- 
tardation of the one, the other also moves quicker or 

The second Dialogue is appropriated chiefly to the dis- 
cussion of the diurnal motion of the earth; and the princi- 
pal arguments urged by Aristotle, Ptolemy, and others, 
are successively brought forward and confuted. The op- 
posers of the earth's diurnal motion maintained, that if it 
were turning rouad, a stone dropped from the top of a 
tower would not fall at its foot ; but, by the rotation of 
the earth to the eastward, carrying away the tower with it, 
would be left at a great distance to the westwai^d ; it 
was common to compare this effect to a stone dropped 
from the mast-head of a ship, and without any regard to 
truth it was boldly asserted that this would fall consider- 
ably nearer the stern than the foot of the mast, if the 
ship were in rapid motion. The same argument was 
presented in a variety of forms, — ^such as that a cannon- 
ball shot perpendicularly upwards would not fall at the 

206 LIFE or GALILEO. : 

same spot ; that if fired to the eastward it would fly far- 
ther than to the westward; that a mark to the east or | 
west w^ould never be hit, because of the rising or sinking I 
of the horizon during the flight of the ball ; that ladies^ i 
ringlets w-ould all stand out to the w^estw^ard, with other I 
conceits of the like nature : to which the general reply is ' 
given, that in all these cases the stone, or ball, or other 
body, participates equally in the motion of the earth, 
which, therefore, so far as regards the relative motion of | 
its parts, may be disregarded. The manner in which I 
%is is illustrated, appears in the following extract from the j 
dialogue : — Sagredo. If the nib of a writing pen which ; 
was in the ship during my voyage direct from Venice to ' 
Alexandria, bad had the power of leaving a visible mark 
of all its path; what trace, what mark, what line would i 
it have left .^ — "Simplicio, It would have left a line | 
stretched out thither from Venice not perfectly straight, | 
or to speak more correctly, not perfectly extended in an ^ 
exact circular arc, but here and there more and less cur- 
ved accordingly as the vessel had pitched more or less ; j 
but this variation in some places of one or two yards to ! 
the right or left, or up or down in a length of many hun- i 
dred miles, would have occasioned but slight alteration ! 
in the whole course of the line, so that it w^ould have been . 
hardly sensible, and without any great error we may ^ 
speak of it as a perfectly circular arc. — Sag. So that the I 
true and most exact motion of the point of the pen w^ould \ 
also have been a perfect arc of a circle if the motion of ! 
the vessel, abstracting from the fluctuations of the weaves, j 
had been steady and gentle ; and if I had held this pen i 
constantly in my hand, and had merely moved it an inch j 


or two one way or the other, what alteration would that 
have made m the true and principal motion ? — SimpL 
Less than that which would be occasioned in a line a 
thousand yards long, by varying here and there from per- 
fect straightness by the quandty of a flea's eye. — SagrecL 
If then a painter on our quitting the port had begun to 
draw with this pen on paper, and had continued his draw- 
ing till w^e got to Alexandria, he would have been able by 
its motion, to produce an accurate representation of many, 
objects perfecdy shadowed, and filled up on all sides with 
landscapes, buildings, and animals, although all the true, 
real, and essential motion of the point of his pen would 
have been no other but a very long and very simple line ; 
end as to the peculiar work of the painter, he would have 
drawn it exactly the same if ther ship had stood still. 
Therefore, of the very protracted motion of the pen, 
there remain no other trace's than those marks drawn 
upon the paper, the reason of this being that the great 
motion from Venice to Alexandria was common to the 
paper, the pen, and everything that was in the ship ; but 
the trifling modon forwards and backwards to the right and 
left, communicated by the painter's fingers to the pen, 
and not to the paper, from being pecuhar to the pen left 
its mark upon the paper which as to this modon was 
immovable. Thus it is likewise true that in the sup- 
position of the earth's rotation, the motion of a falling 
stone is really a long track of many hundreds and thou- 
sands of yards ; and if it could have dehneated its course 
in the calm air, or on any other surface, it would have 
left behind it a very long transversal line ; but that part 
of aU this motion which is common to the stone, the 


tower, and ourselves, is imperceptible by us and the ; 
same as if not eKisting, and only that part remains to be ! 
observed of which neither we nor the tower partake, 
which in short is the fall of the stone along the tower." 

The mechanical doctrines introduced into this second 
Dialouge will be noticed on another occasion ; we shall 
pass on to other extracts, illustrative of the general char- 
acter of Galileo's reasoning: '^ Salviati, I did not 

say that the earth has no principle, either internal or ex- 
ternal, of its motion of rotation, but I do say that I know 
not which of the two it has, and that my ignorance has \ 
no power to take its motion away ; but if this author ] 
knows by what principle other mundane bodies, of the ; 
motion of which we are certain, are turned round, I say ; 
that what moves the Earth is something like that by 
which Mars and Jupiter, and, as he beheves, the starry | 
sphere, are moved round ; and if he will satisfy me as to i 
the cause of their motion, I bind myself to be able to tell j 
him what moves the earth. Nay more ; I undertake to i 
do the same if he can teach me what it is which moves | 
the parts of the earth downwards. — SimpL The cause i 
of this effect is notorious, and every one knows that it is j 
Gravity.- — Salv. You are out. Master Simplicio ; you 
should say that every one knows that it is called Gravity ; ^ 
but I do not ask you the name but the nature of the thing, 1 
of which nature you do not know one tittle more than you ! 
know of the nature of the moving cause of the rotation of i 
the stars, except it be the name which has been given to 
the one, and made familiar and domestic, by the frequent \ 
experience we have of it many thousand times in a day ; i 
but of the principle or virtue by which a stone falls to the ^ 


■ground, we really know no more than we know of the 
principle which carries it upwards when thrown into 
the air, or which carries the moon round its orbit, except 
as I have said, the name of gravity which we have pecu- 
liarly and exclusively assigned to it ; whereas we speak 
of the other with a more generic term, and talk of the 
virtue impressed, and call it either an assisting or an in- 
forming intelligence, and are content to say that Nature 
is the cause of an infinite number of other motions." 

Simplicio is made to quote a passage from Scheiner's 
book of Conclusions against Copernicus, to the follow- 
ing effect : — '^ ' If the whole earth and water were anni- 
hilated, no hail or rain would fall from the clouds, but 
would only be naturally carried round in a circle, nor 
would any fire or fiery thing ascend, since, according to 
the not improbable opinion of these others, there is no 
fire in the upper regions.'— Safe. The foresight of this 
philosopher is most admirable and praiseworthy, for he 
is not content with providing for things that might happen 
during the common course of nature, but persists in 
showing his care for the consequences to what he very 
well knows will never come to pass. Nevertheless, for 
ihe sake of bearing some of his notable conceits, I will 
grant that if the earth and water were annihilated there 
would be no more hail or rain, nor would fiery matter 
ascend any more but would continue a motion of revolu- 
tion. What is to follow ? What conclusion is the phi- 
losopher going to draw ? — SimpL This objection is in 
the very next words — ' Which nevertheless (says he) is 
contrary to experience and reason.' — Safe, Now I 
must yield : since he has so great an advantage over me 




as experience, with which I am quite unprovided. For | 
hitherto I have never happened to see the terrestrial , 
earth and water annihilated, so as to be able to observe 
what the hail and fire did in the confusion. But does he ^ 
tell us for our information at least what they did ? — Simp. 
No, he does not say any thing more. — Salv, I would ' 
give something to have a word or two with this person, | 
to ask him whether, w^hen this globe vanished, it also I 
carried away the common centre of gravity, as I fancy ' 
it did, in which case I take it that the hail and w^ater \ 
would remain stupid and confounded amongst the clouds, 
without knowing what to do with themselves. . . . And j 
lastly, that I may give this philosopher a less equivocal | 
answer, I tell liim that I know as much of what would ! 
follow after the annihilation of the terrestrial globe, as he ' 
could have known what was about to happen in and about j 
it, before it was created." 

Great part of the thK^d Dialogue is taken up with dis- ' 
cussions on the par^ax of the new stars of 1672 and' 
1604, in which Delambre notices that Gallileo does not^ 
employ logarithms in his calculations, although their use I 
had been known since Napier discovered them in 1616 ;: 
the dialogue then turns to the annual motion '' first taken i 
from the Sun and conferred upon the Earth by Aristar-" 
chus Samius, and afterwards by Copernicus." Salviatij 
speaks of his contemporary philosophers with great con-j 
tempt — ^'' If you had ever been worn out, as I have been] 
many and many a time, with hearing what sort of stuff is 
sufficient to make the obstinate vulgar unpersuadable, 
do not say to agree with, but even to Hstento these nov-j 
elties, I believe your wonder at finding so few follower^ 



of these opinions would greatly fall off. But little regard 
in my judment is to be bad of tbose understandings who 
are convinced and immovably persuaded of the fixed- 
ness of the earth, by seeing that they are not able to 
breakfast this morning at Constantinople, and sup in the 
evening in Japan, and who feel satisfied that the earth, 
so heavy as it is, cannot climb up above the sun, and 
then tumbling in a breakneck fashion down again !"^ 
This remark serves to introduce several specious argu- 
ments against the annual motion of the earth, which are 
successively confuted, and it is shewn how readily the 
apparent stations and retrogradations of the planets are 
accounted for on this supposition. 

The following is one of the frequently recurring passa- 
ges in which Galileo, whilst arguing in favor of the enor- 
mous distances at which the theory of Copernicus neces- 
sarily placed the fixed stars, inv^ghs against the arro- 
gance with which men pretend to judge of matters remov- 
ed above their comprehension. '' SimpL All this is 
very well, and it is not to be denied that the heavens may 
surpass in bigness the capacity of our imaginations, as 
also that God might have created it yet a thousand times 
larger than it really is, but we ought not to admit any- 
thing to be created in vain, and useless in the universe. 
Now whilst we see this beautiful arrangement of the 
planets, disposed round the earth at distances propor- 

* The notions commonly entertained of * up' and ' down,' as]connected with 
the observer's own situation, had long been a stumbling-block in the way of 
the new doctrines. When Columbus held out the certainty of arriving in 
India by sailing to the westward on account of the earth's roundness, it was 
gravely objected, that it might be well enough to sail down to India, but that 
the chief difficulty would consist in climbing up back. 


tioned to the effects they are to produce on us for our 
benefit, to what purpose should a vast vacancy be after- 
wards interposed between the orbit of Saturn and the 
starry spheres, containing not a single star, and altogeth- 
er useless and unprofitable ? to what end ? iot whose 
use and advantage ?—Salv, Methinks we ai'^ogate too 
much to ourselves, Simplicio, when we will have it that 
the care of us alone is the adequate and sufficient work 
and bound, beyond which the divine wisdom and power 
does and disposes of nothing. I feel confident that noth- 
ing is omitted by the Divine Providence of what con- 
cerns the government of human affairs ; but that there 
may not be other things in the universe dependant upon 
His supreme wisdom, I cannot for myself, by what my 
reason holds out to me, bring myself to believe. So 
that when I am told of the uselessness of an immense 
space interposed between the orbits of the planets and 
the fixed stars, empty and valueless, I reply that there is 
temerity in attempting by feeble reason to judge the work 
of God, and in calhng vain and superfluous every part of 
the universe which is of no use to us. — Sagr. Say 
rather, and I believe you would say better, that we have 
no means of knowing what is of use to us ; and I hold 
it to be one of the greatest pieces of arrogance and folly 
that can be in this world to say, because I know not of 
what use Jupiter or Saturn are to me, that therefore 
these planets ai-e superfluous ; nay more, that there are 
no such things in nature. To understand what effect is 
worked upon us by this or that heavenly body (since you 
wdll have it that all their use must have a reference to us), 
it would be necessary to remove it for a while, and thei:^ 


the effect which I find no longer produced in me, I may 
say that it depended upon that star. Besides, who will 
dare say that the space which they call too vast and use- 
less between Saturn and the fixed stars is void of other 
bodies belonging to the universe. Must it be so because 
we do not see them : then I suppose the four Medicean 
planets, and the companions of Saturn, came into the 
heavens when we first began to see them, and not be- 
fore ! and, by the same rule, the other innumerable fixed 
stars did not exist before men saw them. The nebute 
were till lately only white flakes, till whh the telescope 
we have made of them constellations of bright and beau- 
tiful stars. Oh presumptuous ! rather, Oh rash igno- 
rance of man. 

After a discussion on Gilbert's Theory of Terrestial 
Magnetism, introduced by the parallelism of the earth's 
axis, and of which Galileo praises very highly both the 
method and results, the dialogue proceeds as follows : — 
'^ SimpL It appears to me that Sig. Salviati, with a fine 
circumlocution, has so clearly explained the cause of 
these effects, that any common understanding, even 
though unacquainted with science, may comprehend it : 
but we, confining ourselves to the terms of art, reduce 
the cause of these and other similar natural phenomena 
to synjfmthy, Vhich is a certain agreement and mutual 
appef^cy arising between things which have the same 
qualities, just as, on the other hand, that disagreement 
and aversion, with which other things naturally repel 
and abhor each other, we style antipathy. — Sagredo, 
And thus with these two words they are able to give a 
reason for the great number of effects and accidents 


which we see not without admiration, to be produced 
in Nature. But it strikes me that this mode of philoso- 
phising has a great sympathy with the style in which one 
of my friends used to paint : on one part of the canvass 
he would write with chalk — there I will ha\^ a fountain 
with Diana and her nynpfphs ; here some hamers : in this 
corner I will have a hunstman, with a stag's head. ; the 
rest may be a landscape of wood and mountain ; and 
what remains to be done may be put in by the color- 
man ; and thus he flattered himself that he had painted 
the story of Actaeon, having contributed nothing to it be- 
yond the names." 

The fourth Dialogue is devoted entirely to an exami- 
nation of the tides, and is a development and extension 
of the treatise already mentioned to have been sent to 
the Archduke Leopold, in 1618. Galileo was uncom- 
monly partial to his theory of the tides, from which he 
thought to derive a direct proof of the earth's motion in 
her orbit ; and although his theory was erroneous, it re- 
quired a farther advance in the science of motion than 
had been attained even at a much later period to point out 
the insufficiency of it. It is well known that the problem 
of explaining the cause of this alternate motion of the 
waters had been considered from the earhest ages one 
of the most difficult that could be proposed, and the so- 
lutions with which different inquirers were obliged to rest 
contented, shew that it long deserved the name given to 
it, of ''the grave of human curiosity." RiccioH has 
enumerated several of the opinions which in turn had 
their favorers and supporters. One party supposed the 
rise of the waters to be occasioned by the influx of 


rivers intojhe sea ; others compared the earth to a large 
animal, of which the tides indicated the respiration ; a 
third theory supposed the existence of subterraneous 
fires, by which the sea was periodically made to boil ; 
others attributed the cause of a similar change of temper* 
rature to the sun and moon. 

There is an unfounded legend that Aristotle drowned 
himself in despair of being able to invent a plausible 
explanation of the extraordinary tides in the Euripus. 
His curiosity on the subject does not appear to have been 
so acute (judging from his writings) as this story would 
imply. In one of his books he merely mentions a ru- 
mor, that there are great elevations or swellings of the 
seas, which recur periodically, according to the course 
of the moon. Lalande, in the fourth volume of his As- 
tronomy, has given an interesting account of the connec- 
tion of the tides with the moon's motion. Pytheas of 
Marselles, a contemporary of Aristotle, was the first who 
has been recorded as observing, that the full tides oc- 
cur at full moon, and the ebbs at new moon. This is 
not quite correctly stated ; for the tide of new moon is 
known to be still higher than the rise at the full, but it is 
likely enough, that the seeming inaccuracy should be 
attributed, not to Pytheas, but to his biographer Plutarch, 
who, in many instances, appears to have viewed the 
opinions of the old philosophers through the mist of his 
own prejudices and imperfect information. The fact is, 
that on the same day when the tide rises highest, it also 
ebbs lowest ; and Phytheas, who, according to Pliny, 
J had recorded a tide in Britain of eighty cubits, could not 
i have been ignorant of this. Posidonius, as quoted by 


Strabo, maintained the existence of three periods of the 
tide, daily, monthly, and annual, ^'in sympathy with the 
moon." Pliny, in his vast collection of natural obser- 
vations, not unaptly styled the Encyclopaedia of the 
Antients, has the following curious passages: — ^'The 
flow and ebb of the tide is very wonderful ; it happens 
in a variety of ways, but the cause is in the sun and 
moon." He then very accurately describes the course 
of the tide during a revolution of the moon, and adds: 
'' The flow takes place every day at a different hour ; 
being waited on by the star, which rises every day in 
a different place from that of the day before, and with 
greedy draught drags the seas with it." ''When the 
moon is in the north, and further removed from the 
earth, the tides are more gentle "than when digressing 
to the south she exerts her force with a stronger ef- 

The College of Jesuits at Coimbra, appears to deserve 
the credit of first clearly pointing out the true relation 
between the tides and the moon, which was also main- 
tained a few years later by Antonio de Dominis and 
Kepler. In the Society's commentary on Aristotle's 
book on Meteors, after refuting the notion that the tides 
are caused by the light of the sun and moon, they s^, 
" It pppears more probable to us, without any rai^ac- 
tion, of which there appears no need or indication, 
that the moon raises the waters by some inherent pow- 
er of impulsion, in the same manner as a magnet moves 
iron ; and according to its different aspects and approa- ^ 
ches to the sea, and the obtuse or acute angles of its 
bearing, at one time to attract and raise the waters ■ 


along the shore, and then again to leave them to sink 
down by their own weight, and to gather into a lower 
level." The theory of Universal Gravitation seems here 
within the grasp of these philosophers, but unfortunate- 
ly it did not occur to them that possibly the same at- 
traction might be exerted on the earth as well as the 
water, and that the tide was merely an effect of the 
diminution of force, owing to the increase of distance, 
with which the centre of the earth is attracted, as com- 
pared with that exerted on its surface. This idea so 
happily seized afterwards by Newton^ might at once 
have furnished them with a satisfactory explanation of 
the tide, which is observed on the opposite side of the 
earth as well as under the moon. They might have 
seen that in the latter case the centre of the earth is 
pulled away from the water, just as in the former the 
water is pulled away from the centre of the earth, the 
sensible effect to us being precisely the same. For want 
of this generalization, the inferior tide, as it is called, 
presented a formidable obstacle to this theory, and the 
most plausible explanation that was given was, that this 
magnetic virtue radiated out from the moon, was re- 
flected by the solid heavens, and concentrated again as 
in a focus on the opposite side of the earth. The ma- 
jority of modern astronomers who did not admit the ex- 
istence of any solid matter fit for producing the effect 
assigned to it, found a reasonable difficulty in acquiescing 
in this explanation. Galileo, who mentions the Arch- 
bishop of Spalatro's book, treated the theory of attrac- 
tion by the moon as absurd. " This motion of the seas 
is local and sensible, made in an immense mass of water, 



and cannot be brought to obey light, and warmth, and 
predominancy of occult qualities, and such like vain fan- 
cies ; all which are so far from being the cause of the i 
tide, that on the contrary the tide is the cause of them, 
inasmuch as it gives rise to those ideas in brains which \ 
are more apt for talkativeness and ostentation, than for ; 
speculation and inquiry into the secrets of Nature ; who, i 
rather than see themselves driven to pronounce these i 
wise, ingenuous and modest words — / do not know — 
will blurt out from their tongues and pens all sorts of 
extravagance." \ 

Galileo's own theory is introduced by the following il- \ 
lustration, which indeed probably suggested il, as he was 
in the habit of suffering no natural phenomena, however ' 
trivial in appearance, to escape him. He felt the ad- i 
vantage of this custom in being furnished on all occasions : 
with a stock of homely observations, to which the daily j 
experience of his hearers readily assented, and which j 
he could show to be identical in principle with the phe- j 
nomena under discussion. That he was mistaken in 
applying his observations in the present instance can- J 
not be urged against the incalculable value of such a I 

'^ We may explain and render sensible these effects by ; 
the example of one of those barks which come continu- 
ally from Lizza Fusina, with fresh water for the use of 
the city of Venice. Let us suppose one of these barks 
to come thence with moderate velocity along the canal, 
carrying gently the water with which it is filled, and then j 
either by touching the bottom, or from some other hin- j 
drance which is opposed to it, let it be notably retarded ; 1 


the water will not on that account lose like the bark the 
impetus it has already acquired, but wiU forthwith run on 
towards the p^pow where it will sensibly rise and be de- 
pressed at the stern. If on the contrary the said vessel 
in the middle of its steady course shall receive a new and 
sensible increase of velocity, the contained water before 
giving into it will persevere for some time in its slowness, 
and will be left behind, that is to say towards the stern, 
where consequently it will rise, and sink at the head. — 
Now, my masters, that which the vessel does in respect 
of the water contained in it, and that which the water 
does in respect of the vessel containing it, is the same to 
a hair as what the Mediterranean vase does in respect of 
the water which it contains, and that the waters do in 
respect of the Mediterranean vase which contains them. 
We have now only to demonstrate how, and in what 
manner it is true that the Mediterranean, and all other 
gulfs and in short all the parts of the earth move witli a 
motion sensibly not uniform, although no motion results 
thence to the whole globe which is not perfectly uniform 
and regular." 

This uneqnable motion is derived from a combination 
-of the earth^'s motion on her axis, and in her orbit, the 
consequence of which is, that a point under the sun is 
carried in the same direction by the annual and diurnal 
velocities, whereas a point on the opposite side of the 
globe is carried in opposite directions by the annual and 
diurnal motions, so that in every twenty-four hours the 
y absolute motion through space of every point in the earth 
completes a cycle of varying swiftness. Those readers 
who are unacquainted with the mathematical theory of mo- 
tion must be satisfied with the assurance that this spe- 


cions representation is fallacious, and that the oscillation 
of the water does not in the least result from the causes ' 
here assigned to it : the reasoning necessary to prove i 
this is not elementary enough to be introduced here with ; 
propriety. \ 

Besides the principal daily oscillation of the water^ ! 
there is a monthly inequality in the rise and fall, of which 
the extremes are called the spring and neap tides ; the 
manner in which Galileo attempted to bring his the- 
ory to bear upon these phenomena is exceedingly curi- 
ous. j 

'^ It is a natural and necessary truth, that if a body be i 
made to revolve, the time of revolution will be greater iii 
3. greater circle than in a less : this is universally allow- • 
ed, and fully confirmed by experiments, such for instance 
as these : — In wheel clocks, especially in large ones, to \ 
regulate the going, the workmen fit up a bar capable of \ 
revolving horizontally, and fasten two leaden weights to I 
the ends of it ; and if the clock goes too slow by merely^ j 
approaching these w^eights somewhat towards the centre 
of the bar, they make its vibrations more fi'equent^, at \ 
w^hich times they are moving in smaller circles than be- i 
fore. — Or, if you fasten a weight to a cord which you ; 
pass round a pulley in the ceiling, and whilst the weight i 
is vibrating draw in the cord towards you, the vibrations : 
will become sensibly accelerated as the length of the ,^ 
string diminishes. We may observe the same rule to 3 
hold among the celestial motions of the planets, of -j 
which we have a ready instance in the Medicean planets,. | 
which revolve in such short periods round Jupiter. We j 
may therefore safely conclude, that if the moon for in- ] 
stance shall continue to be forced round by the same , 


moving power, and were to move in a smaller circle, it 
would shorten the time of its revolution. Now this very 
thing happens in fact to the moon, which I have just ad- 
vanced on a supposition. Let us call to mind that we 
have already concluded with Copernicus, that it is impos- 
sible to separate the moon from the earth, round wliich, 
without doubt it moves in a month : we must also re- 
member that the globe of the earth, accompanied always 
by the moon, revolves in the great circle round the sun 
in a year, in w^hich time the moon revolves round the 
earth about thirteen times, wdience it follows that the 
moon is sometimes near the sun, that is to say between 
the earth and sun, sometimes far from it, when she is on 
the outside of the earth. Now if it be true that the power 
which moves the earth and the moon round the sun re- 
mains of the same efficacy, and if it be true that the same 
movable, acted on by the same force, passes over sim- 
ilar arcs of circles in a time which is least when the cir- 
cle is smallest, we are forced to the conclusion thai ?/ 
new moon, w^hen in conjunction with the sun, the moon 
passes over greater arcs of the orbit round the sun, than 
when in opposition at full moon ; and this inequality of 
the moon will be shared by the earth also. So that ex- 
actly the same thing happens as in the balance of the 
clocks ; for the moon here represents the leaden weight, 
which at one time is fixed at a greater distance from the 
centre to make the vibrations slow^er, and at another time 
nearer to accelerate them." 

Wallis adopted and improved this theorj^ in a paper 

which he inserted in the Philosophical Transactions for 

1'666, in which he declares, that the circular motion 

round the sun should be considered as taking place at a 

T 2 


point which is the centre of gravity of the earth and moori^ 
'' To the first objection, that it appears not how two 
bodies that have no tie can have one common centre of 
gravity, I shall only answer, that it is harder to show 
how they have it, than that they have it." As Wallis 
was perfectly competent from the time at which he livedo 
and his knowledge of the farthest advances of science in 
his time, to appreciate the value of Galileo's writings, 
we shall conclude this chapter with the judgment that he 
has passed upon them in the same paper. '' Since Gal- 
ileo, and after him Torricelh and others have applied me- 
chanical principles to the solving of philosophical diffi- 
culties, natural philosophy is well known to have been 
rendered more intelligible, and to have made a much 
greater progress in less than a hundred years than before 
for many ages/^ 

C H A P T E R XV: 

Galileo at Arcetri—BecomesBlind — 3Ioon^s Lihration — 
Publication oftlie Dialogues on Motion. 

We have already alluded to the im.perfect state of the 
knowledge possessed wdth regard to Galileo's domestic 
life and personal habits ; thei-e is reason how^ever to think 
that unpubUshed materials exist from w hich these out- 
lines, might be in part filled up. Venturi informs v^> 
that he had seen in the collection fi:om which he derived 



a great part of the substance of his Memoirs of Galileo, 
about one hundred and twenty manuscript letters, dated 
between the years J 623 and 1633, addressed to him by 
his daughter Maria, who wdth her sister had attached 
herself of the convent of St. Matthew, close to Galileo's 
usual place of residence. It is difficult not to think that 
much interesting information might be obtained from 
these, with respect to Galileo's domestic character. 
The very few published extracts confirm our favorable 
impressions of it, and convey a pleasing idea of this his 
favorite daughter. Even when, in her affectionate ea- 
gerness to soothe her father's wounded feehngs at the 
close of his imprisonment in Rome, she dwells with de- 
light upon her hopes of being allow^ed to reheve him, by 
taking on herself the penitential recitations which formed 
a part of his sentences, the prevalent feeling excited in 
every one by the perusal must surely be sympathy with 
the filial tenderness which it is impossible to misunder- 

The joy she had anticipated in again meeting her pa- 
rent, and in compensating to him by her attentive affec- 
tion the insults of his malignant enemies, w^as destined 
to be but of short duration. Almost in the same month 
in which Gahleo returned to Arcetri she was seized with 
a fatal illness ; and already in the beginning of April, 
1 634, we learn her death from the fruitless condolence 
of his friends. He was deeply and bitterly affected by 
this additional blow which came upon him when he was 
himself in a weak and declining state of health, and his 
answ^ers breathe a spirit of the most hopeless and gloomy 


In a letter written in April to Bocchineri, his son's 
father-in-law, he says : '^ The hernia has returned worse 
than at first : my pulse is intermitting, accompanied with 
a palpitation of the heart ; an immeasureable sadness and 
melancholy and entire loss of appetite ; I am hateful to 
myself ; and in short I feel that I am called incessantly 
by my dear daughter. In this state, I do not think it 
advisable that Vincenzo should set out on his journey, 
and leave me, when every hour something may occur, 
which would make it expedient that he should be here." 
In this extremity of ill health, Gahleo requested leave 
to go to Florence for the advantage of medical assist- 
ance ; but far from obtaining permission, it w^as intimat- 
ed that any additional importunities would be noticed by 
depriving him of the partial liberty he was then allowed 
to enjoy. After several years confinement at Arcetri, 
during the whole of which time he suffered from con- 
tinual indisposition, the inquisitor Fariano wrote to him 
in 1638, that the pope permitted his removal to Flor- 
ence, for the purpose of recovering his health : requir- 
ing him at the same time to present himself at the Of- 
fice of the Inquisition, where he would learn the con- 
ditions on which this favor had been granted. These 
were that he should neither quit his house nor receive 
his friends there ; and so closely was the letter of these 
instructions adhered to, that he was obliged to obtain a 
special permission to go out to attend mass during Pas- 
sion w^eek. The strictness with which all personal in- 
tercourse with his friends was interrupted, is manifest 
from the result of the following letter from the duke of 
Tusc^y's secretary of state to Nicolini, his ambassador 
at Rome. '' Signor Galileo Gahlei, from his great age 

i i 


and the illnesses which afflict him, is in a condition soon 
to go to another world; and although in this the eter- 
nal memory of his fame and value is already secured, 
yet his Highness is greatly desirous diat the world should 
sustain as little loss as possible by his death ; that his la- 
bors may not perish, but for the public good may be 
brought to that perfection which ho will not be able to 
give them. He has in his thoughts many things worthy 
of him, which he cannot be prevailed on to communi- 
cate tc laiy but Father Benedetto CastelH, in whom he 
has entire confidence. His Highness wishes therefore 
that you should see Casteni,and induce him to procure 
leave to come to Florence for a fev/ months for this 
purpose, which his Highness has very much at heart ; 
and if he obtains permission, as his Highness hopes, 
you will furnish him with money and every thing else 
he ma)' require for his journey." Castelh, it will be re^ 
membered, was at this time salaried by the court of 
Rome. Nicolini answered that Castelli had been him- 
self to die Pope to ask leave to go to Florence. Ur- 
ban immediately intimated his suspicions that his design 
was to see Gahleo, and upon Castelli's stating that cer- 
tainly it would be impossible for him to refrain from at- 
tempting to see him, he received permission to visit him 
in the company of an officer of the Inquisition. At the 
end of some months Galileo was remais^ded to Arcetri. 
which he never again quitted. ^ 

In additon to his other infirmities, a disorder which 
some years before had affected the sight of his right eye 
returned in 1636 ; in the course of the ensuing year the 
other eye began to fail also, and in a few months he be- 
came totally bhnd. It would be difficult to find any even 


among those who are the most careless to make a proper 
use of the inv^aluable blessing of sight, who could bear 
unmoved to be deprived of it, but on Galileo the loss 
fell with peculiar and terrible severity ; on him who had 
boasted that he would never cease from using the senses 
which God had given him, in declaring the glory of his 
-works, and the business of whose life had been the splen- 
did fulfilment of that undertaking, '' The noblest eye 
is darkened," said Castelii, '' which nature ever made : 
an eye so privileged, and gifted with such rare qualities^ 
thai it may with truth be said to have seen more than 
all those who are gone, and to have opened the eyes 
of all who are to come." His own patience and resig- 
nation under this fatal calamity are truly wonderful ; 
and if occasionally a word of complaint escaped him, 
it was the chaste^^ed tone of the following expressions — 
^'Alas ! your dear friend and servant Galileo has be- 
come totally and irreparably blind ; so that this heaven, 
this earth, this universe, which with wonderful obser- 
vations I had enlarged a hundred and thousand times 
beyond the belief of by-gone ages, henceforward for 
me is shrunk into the narrow space which I myself fill 
in it.-— So it pleases God : it shall therefore please me 
also." Hopes were at first entertained by Galileo's 
friends, that the bhndness was occasioned by cataracts, 
4md that he naight look forward to rehef from the opera- 
lion of coucnkig ; but it .very soon appeared that the 
disorder was not in the h\]jxiors of the eye, but in the 
cloudiness of the cornea, the symptoms of which all ex- 
ternal remedies failed to alleviate. 

As long as the power was left him, he had indefatiga- 
bly continued his astronomical observations. Just before 


his sight began to decay, he had observed a new phe- 
nomenon in the moon, which is now known by the name 
of the moon's libration, the nature of which we will 
shortly explain. A remarkable circumstance connected 
with the moon's motion is, that the same side is always 
visible from the earth, showing that the moon turns once 
on her own axis in exactly the time of her monthly rev- 
olution.^ But Galileo, who was by this time familiar 
with the whole of the moon's visible surface, observed 
that the above-mentioned effect does not accurately take 
place, but that a small part on either side comes alter- 
nately forward into sight, and then again recedes, accord- 
ing to the moon's various positions in the heavens. 
He was not long in detecting one of the causes of this 
apparent libratory or rocking motion. It is partly occa- 
sioned by our distance as spectators from the centre of 
the earth, which is also the centre of the moon's motion. 
In consequence of this, as the moon rises in the sky we 
get an additional view of the lower half and lose sight of 
a small part of the upper half which was visible to us 
while we were looking down upon her when low in the 
horizon. The other cause is not quite so simple, nor is 
it so certain that Galileo adverted to it : it is however 
readily intelligible even to those who are unacquainted 
with astronomy, if they will receive as a fact that the 
monthly motion of the moon is not uniform, but that she 

* Frisi says that Galileo did not perceive this conclusion ( Elogio del Ga- 
lileo) ; but see the DiaL on the System, Dial. 1. pp. 61, 62, 85. Edit. 1744. 
Plutarch says, (De Placitis Phios. lib ii^ c. 28, ) that the Pythagoreans be- 
lieved the moon to have inhabitants fifteen times as large as men, and that 
their day is fifteen times as long as ours. It seems probable, that the former 
of these opinions was engrafted on tlie latter, which is true, and implies a 
perception of the fact in the text. 


moves quicker at one time than another, whilst the mo- 
tion of rotation on her own axis, like that of the earth, 
is perfectly uniform. A very little reflection will show 
that the observed phenomenon will necessarily follow. 
If the moon did not turn on her axis, every side of her 
would be successively presented, in the course of a 
month, to the earth ; it is the motion of rotation which 
tends to carry the newly discovered parts out of sight. 
Let us suppose the moon to be in that part of her orbit 
where she moves with her average motion, and that she 
is moving towards that part where she mo^es most quick- 
ly. If the motion in the orbit were to remain the same 
all the way round, the motion of rotation would be just 
sufficient at every point to bring round the same part 
of the moon directly in front of ilie earth. But since, 
from the supposed point, the moon is moving for some 
time round the earth with a motion continually growing 
quicker, the motion of rotation is not sufficiently quick 
to carry out of sight the entire part discovered by the 
motion of translation. We therefore get a glimpse of a 
narrow strip on the side from which the moon is moving, 
which strip grows broader and broader, till she passes 
the point where she moves most swiftly, and reaches the 
point of average swiftness on the opposite side of her 
orbit. Her motion is now continually grooving slower, 
and therefore from this point the motion of rotation is too 
swift, and carries too much out of sight, or in other words, i 
brings into sight a strip on the side towards which the ^ 
moon is moving. This increases till she passes the point 
of least swiftness, and arrives at the point from which we '• 
began to trace her course, and the phenomena are re- i 
peated in the same order. i 


This interesting observation closes the long list of 
Galileo's discoveries in the heavens. After his aDJyra- 
tion, h© ostensibly v^ithdrew himself in a great measure 
from his astronomical pursuits, and employed himself till 
1636 principally with his Dialogues on Motion, the last 
work of consequence that he pubHshed. In that year he 
entered into correspondence with the Elzevirs, through 
his friend Micanzio, on the project of printing a complete 
edition of his writings. Among the letters which Mican- 
zio wrote on the subject, is one intimating that he had 
enjoyed the gratification, in his quality of Theologian to 
the Repubhc of Venice, of refusing his sanction to a 
work written against Galileo and Copernicus. The tem- 
per however in which this refusal was announced, 
contrasts singularly with that of the Roman Inquisi- 
tors. ''A book was brought to me which a Veronese 
Capuchin has been writing, and wished to print, deny- 
ing the motion of the earth. I was inclined to let it go, to 
make the world laugh, for the ignorant beast entitles eve- 
ry one of the twelve arguments which compose his book, 
'an irrefragable and undeniable demonstration,' and then 
adduces nkhing but such childish trash as every man of 
sense has long discarded. For instance, this poor animal- 
understands so much geometry and mathematics, that he 
brings forward as a demonstration, that if the earth could 
move, having nothing to support it, it must necessarily 
fall. He ought to have added, thai then we should catch 
all the quails. But when I saw that he speaks indecently 
of you, and has had the impudence to put down an ac- 
count of what passed lately, saying ihat he is in possession 
of the whole of your process and sentence, I desired the 
man who brought it to me to go and be hanged. But you 


know the ingenuity of impertinence ; I suspect he will 
succeed elsewhere, because he is so enamored of his ab- 
surdities, that he believes them more firmly than his 

After Galileo's condemnation at Rome, he liad been 
placed by the Inquisition in the hst of authors the whole 
of whose writings, ' edita et edenda ' were strictly forbid- 
den. Micanzio could not even obtain permission lo re- 
print the essay on Floating Bodies, in spite of his protes- 
tations that it did not in any way relate to the Copernican 
theory. This was the greatest stigma with which the 
Inquisition were in habit of branding obnoxious authors ; 
and, in consequence of it, when Galileo had completed 
his Dialogues on Motion, he found great difficulty in 
contriving their publication, the nature of which may be 
learned from the account which Pieroni sent to Galileo 
of his endeavors to print them in Germany. He first 
took the manuscript to Vienna, but found that every book 
printed there must receive the approbation of the Jesuits ; 
and Galileo's old antagonist, Scheiner, happening to be 
in that city, Pieroni feaiied lest he should interfere to pre- 
vent the pubhcation altogether, if the knowledge of it 
should reach him. Through the intervention of Cardinal 
Dietrichstein, he therefore got permission to have it print- 
ed at Olmutz, and that it should be approved by a Do- 
minican, so as to keep the whole business a secret from 
Scheiner and his party ; but during this negociation the 
Cardinal suddenly died, and Pieroni being besides dissat- 
isfied with the Olmutz type, carried back the manuscript 
to Vienna,/rrom whence he heard that Scheiner had gone 
into Silvia. A new approbation was there procured, 
and the work was just on the point of being sent to press, 


when the dreaded Scheiaer re-appeared in Vi^tpa, on 
which Pieroni again thought it adv^isable to suspend the 
impression till his departure In the mean time, his own 
duty as a military architect in the Emperor's service car- 
ried him to Pra^ we, where Cardinal Harrach, on a former 
occasion, had offered him the use of the newly-erected 
University press. But Harrach happened not to be at 
Prague, and this plan like the rest became abortive. In 
the mean time Galileo, wearied with these delays, had 
engaged with Louis Elzevir, who undertook to print the 
Dialogues at Amsterdam. 

It is abundantly evident from Galileo's correspondence 
that this edition was printed with his full concurrence, 
although in order to obviate further annoyance, he pre- 
tended that it was pirated from a manuscript copy which 
he sent into France to the Compte de Noailles, to whom 
the work is dedicated. The same dissimulation had been 
previously thought necessary, on occasion of the Latin 
translation of '' The Dialogues on the System,'' by Ber- 
negger, which Galileo expressly requested through his 
friend Deodati, and of which he more than once 
privately signified his approbation, presenting the trans- 
lator with a valuable telescope, although he pubhcly p o- 
tested against its appearance. The story which Berneg- 
ger introduced in his preface, tending to exculpate Gahleo 
from any share in the publication, is by his own confes- 
sion a mere fiction. Noailles had been ambassador at 
Rome, and, by his conduct there, well deserved the 
compliment which Galileo paid him on the present occa- 

As an introduction to the account of this work, which 
Galileo considered the best he had ever produced, it will 


become necessaiy to premise a slight sketch of the na- 
ture of the mechanical philosophy which he found pre- 
vaihng, nearly as it had been delivered by Aristotle, with 
the same view with which we introduced specimens of 
of the astronomical opinions current when Galileo began 
to write on that subject : they serve to show^ the nature 
and objects of the reasoning which he had to oppose ; 
and, without some exposition of them, the aim and value 
of many of his arguments would be imperfectly under-- 
stood and appreciated. 


State of the Science of 3Iotion before Galileo. 

It is generally difficult to trace any branch of human 
knowledge up to its origin, and more especially when, as 
in the case of mechanics, it is very closely connected 
with the immediate wants of mankind. Little has been 
told to us when we are informed that so soon as a man 
might wish to remove a heavy stone, ^'he would be led, 
by natural instinct, to slide under it the end of some long 
instrument, and that the same instinct would teach him 
either to raise the further end, or to press it downwards, 
so as to turn round upon some support placed as near to 
the stone as possible." 

Montucla's histor)^ would have lost nothing in value, iL 


omitting '' this philosophical view of the birth of the art," 
he had contented himself with his previous remark, that 
there can be little doubt that men were familiar with the 
use of mechanical contrivances long before the idea oc- 
curred of enumerating or describing them, or even of ex- 
amining very closely the nature and limits of the aid 
they are capable of affording. The most careless obser- 
ver indeed could scarcely overlook that the weights 
heaved up with a lever, or rolled along a slope into their 
intended places, reached them more slowly than those 
which the workmen could lift directly in their hands ; 
but it probably needed a much longer time to enable them 
to see the exact relation which, in these and all other ma- 
chines, exist between the increase of the power to move 
and the decreasing swiftness of the thing moved. 

In the preface to Galileo's Treatise on Mechanical 
Science, published in 1592, he is at some pains to set 
in a clear light the real advantages belonging to the use 
of machines, '' which (says he) I have thought it neces- 
sary to do, because, if I mistake not, I see almost all 
mechanics deceiving themselves in the behef that, by 
the help of a machine, they can raise a greater weight 
than they are able to lift by the exertion of the same force 
without it. — Now if we take any determinate weight, end 
any force, and any distance whatever, it is beyond doubt 
that we can move the weight to that distance by means 
of that force ; because even although the force may be 
exceedingly small, if we divide the weight into a number 
of fragments, each of which is not too much for our force, 
and carry these pieces one by one, at length we shall 
have removed the whole weight ; nor can we reasonably 

say at the end of our work, that this great weight has 



been moved and carried away by a force less than itself, 
unless we add that the force has passed several times over 
the space through which the whole weight has gone but 
once. From which it appears that the velocity of the i 
force, understanding by velocity the space gone through j 
in a given time, has been as many times greater than that of i 
the weight, as the weight is greater than the force : nor can 
we on that account say that a great force is overcome by | 
a small one, contrary to nature : then only might we say | 
that nature is overcome when a small force moves a great i 
weight as swiftly as itself, which we assert to be absolutely i 
impossible with any machine either ah^eady or hereafter ; 
to be contrived. But since it may occasionally happen 
that we have but a small force, and want to move a great \ 
weight without dividing it into pieces, then we must have I 
recourse to a machine by means of which we shall remove ' 
the given weight, with the given force, through the re- \ 
quired space. But nevertheless the force as beiore will i 
have to travel over that very same space as many times 
repeated as the we ght surpasses its powder, so that, at i 
the end of our work, we shall find that we have derived | 
no other benefit from our machine than that we have car- I 
ried away the same weight altogether, which if divided y 
into pieces we could have carried without the machine, ^ 
by the same force, through the same space, in the same 
time. This is one of the advantages of a machine, be- | 
cause it often happens that we have a lack of force but 
abundance of time, and that we wish to move great weights | 
all at once." j 

This compensation of force and time has been fanci- ? 
fully personified by saying that Nature cannot be cheated, , 
and in scientific treatises on mechanics, is called the '^prin- 
ciple of virtual velocities," consisting in the theorem 


that two weights will balance each other on any machine, 
no matter how complicated or intricate the connecting 
contrivances may be, when one weight bears to the other 
the same proportion that the space through which the 
latter would be raised bears to that through which the 
former would sink, in the first instant of their motion, if 
the machine were stirred by a third force. The whole 
theory of machines consists merely in generahzng and 
following out this principle into its consequences ; com- 
bined when the machines are in a siate of motion, with 
another principle equally elementary, but to which our 
present subject does not lead us to allude more particu- 

The credit of making known the principle of virtual 
velocities is universally given to Galileo : and so fai* de- 
servedly, that he undoubtedly perceived the importance of 
it, and by introducing it everywhere into his writings 
succeeded in recommending it to others ; so that five 
and twenty years after his death, BurreUi, who had been 
one of Gallileo's pupils calls it '' that mechanical princi- 
ple v%'ith which everybody is so famihar,'' aud from that 
time to the present it has continued to be taught as an 
elementary truth in most systems of mechanics. But 
although Galileo had the merit in this, as in som^any other 
cases, of familiarizing and reconciling the world to the 
reception of truth, there are remarkable traces before his 
time of the employment of this same principle, some of 
which have been strangely disregarded. Lagrange as- 
serts that the ancients were entirely ignorant of the prin- 
ciple of virtual velocities, although Gahleo, to whom he 
refers it, distinctly mentions that he himself found it in the 
writings of Aristotle. Montucla quotes a passage from 


Aristotle's Physics, in ^vhich the law is stated generally, 
but adds that he did not perceive its immediate applica- 
tion to the lever, and other machines. The passage to 
which Galileo alludes is in Aristotle's Mechanics, where 
in discussing the properties of the lever, he says express- 
ly, ^' the same force will raise a greater weio-ht, in pro- 
portion as the force is applied at a greater distance from 
the fulcrum, and the reason, as I have already said, is 
because it describes a greater circle*^; and a weight 
which is farther removed from the centre is made to 
move through a greater space." 

It is true, that in the last mentioned treatise, Aristotle 
has given other reasons which belong to a very different 
kind of philosophy, and which may lead us to doubt 
whether he fully saw the force of the one we have just 
quoted. It appeared to him not wonderful that so many 
mechanical paradoxes (as he called them) should be 
connected with circular motion, since the circle itself 
seemed of so paradoxical a nature. '' For, in the first 
place, it is made up of an immovable centre, and a mov- 
able radius, qualities w^hich are contrary to each other. 
2dly. Its circumference is both convex and concave. 
3dly, The motion by which it is described is both for- 
ward and backward, for the describing radius comes 
back to the place from which it started. 4thly. The ra- 
dius is one ; but every point of it moves in describing the 
circle with a different degree of swiftness." 

Perhaps Aristotle may have borrowed the idea of vir- 
tual velocities, contrasting so strongly with his other 
physical notions, from some older writer ; possibly from 
Archytas, who we are told was the first to reduce the 
science of mechanics to methodical order ; and who by 


the testimony of his countrymen was gifted with extraor- 
dinary talents, although none of his works have come 
down to us. The other principles and maxims of Aris- 
totle's mechanical philosophy, which we shall have oc- 
casion to cite, are scattered through his books on Me- 
chanics, on the Heavens, and in his Physical Lectures, 
and will therefore follow rather unconnectedly, though 
we have endeavored to arrange them with as much regu- 
larity as possible. 

After defining a body to be that which is divisible in 
every direction, Aristotle proceeds to inquire how it hap- 
pens that a body has only the three dimensions of length, 
breadth, and thickness ; and seems to think he has given 
a reason in saying that, when we speak of two things, 
we do not say '•'- all," but ^' both," and thi^ee is the first 
number of which we say ''all," When he comes to 
speak of motion, he says, '' If motion is not understood, 
we cannot but remain ignorant of Nature. Motion ap- 
pears to be of the nature of continuous quantities, and in 
continuous quantity infinity first maks its appearance ; so 
as to furnish some with a definition who say that contin- 
uous quantity is that which is infinitely divisible. — More- 
over, unless there be time, space, and a vacuum, it is- 
impossible that there should be motion." — Few propo- 
sitions of Aristotle's physical philosophy are more noto- 
rious than his assertion that nature abhors a vacuum, on 
which account his last passage is the more remarkable, as 
he certainly did not go so far as to deny the existence of 
motion, and therefore asserts here the necessity of that 
of which he afterwards attempts to show the absurdity. — 
'' Motion is the energy of what exists in power so far 
forth as so existing. It is that act of a movable which 


belongs to its power of moving."* After struggling 
through such passages as the preceding we come at last 
to a resting-place. — '' It is difficult to understand what 
motion is." — When the same question was once pro- 
posed to another Greek philosopher, he walked away, 
saying, '' I cannot tell you, but I will show you ;" an 
^nswer intrinsically worth more than all the subtleties of 
I Aristotle, who was not humble-minded enough to discov- 
/ er that he was tasking his genius beyond the limits mark- 
ed out for human comprehension. 
*^-v. He labors in the same manner and with the same suc- 
cess to vary the idea of space. He begins the next 
book with declaring that ^' those who say there is a vac- 
uum assert the existence of space ; for a vacuum is space 
in which there is no substance ;" and after a long and 
tedious reasoning concludes that, ''not only what space 
is, but also whether there be such a thing cannot but be 
doubted." Of time he is content to say merely, that 
^' it is clear that time is not motion, but that without 
motion there would be no time ;" and there is perhaps 
little fault to be found with this remark, understanding 

* Lib. iii. c. 2. The Aristotelians distinguished between tilings us ex- 
isting in act or energy and things in capacity or power. For the advantage 
of those who may think the distinction worth attending to, we give an illus- 
ti'ation of Aristotle's meaning, from a very acute andjearned commentator : 
— " It (motion) is something more than dead capacity ; something less than 
perfect actuality ; capacity roused, and striving to quit its latent character ; 
not the capable brass, nor yet the actual statue, but the capacity in energy ; 
that is to say, the brass in fusion, while it is becoming tiie statue, and is not 
yet become." — " The bow moves not because it may be bent, nor because it 
is bent ; but the motion lies between ; lies in an imperfect and obscure union 
of the two together ; is the actuality (if I may so say) even of capacity itself; 
imperfect and obscure, because such is capacity to which it belongs."' — Har- 
ris, Philosophical Arrangements, 


motion in the gennral sense in which Aristotle here ap- 
plies it, of every description of change. 

Proceeding after these remarks on the nature of mo- 
tion in general to the motion of bodies, we are told that 
'' all local motion is either straight, circular, or com- 
pounded of these two ; for these two are the only simple 
sorts of motion. Bodies are divided into simple and 
concrete ; simple bodies are those which have naturally 
a principle of motion, as fire and earth, and their kinds. 
By a simple motion is meant the motion of a simple body. 
By these expressions Aristotle did not mean that a sim- 
ple body cannot have what he calls a compound motion, 
but in that case he called the motion violent or unnatu- 
ral ; this division of motion into natural and violent runs 
through the whole of the mechanical philosophy founded 
upon his principles. '' Circular motion is the only one 
which can be endless ;" the reason of which is given in 
another place : for ^' that cannot be doing which cannot 
be done ; and therefore it cannot be that a body should 
be moving towards a point (i. c. the end of an infinite 
straight line) whither no motion is sufficient to bring it." 
Bacon seems to have had these passages in view w^hen he 
indulged in the reflections which we have quoted in page 
51. '' There are four kinds of motion of one thing by 
another : Drawing, Pushing, Carrying, Rolling. Of 
these, Carrying and Rolling may be referred to Drawing 
and Pushing. — The prime mover and the thing moved 
1; are always in contact. " 

The principle of the composition of motions is stated 

very plainly : ''when a movable is urged in two direc- 

Itions with motions bearing any ratio to each other it 

I moves necessarily in a straight line which is the diameter 

of the figure formed by drpwing the two lines of di- 


rection of that ratio ;'' and adds, in a singularly curious 
passage, ^'but when it is urged for an indefinitely small 
time with two motions which have an indefinitely small i 
ratio one to another, the motion cannot be straight, so 
that a body describes a curve, when it is urged by two 
motions bearing an indefinitely small ratio one to another ' 
and lasting an indefinitely small time." ' 

He seemed on the point of discovering some of the ! 
real law^s of motion, when he was led to ask — '' Why 
are bodies in motion more easily moved than those ■ 
which are at rest ? — And why does the motion cease of ' 
things cast into the air ? Is it that the force has ceased « 
which sent them forth, or is there a struggle against the \ 
motion, or is it through the disposition to fall, does it 
become stronger than the projectile force, or is it foolish 
to entertain doubts on this question, when the body has 
quitted the principle of its motion ?" A commentator 
at the close of the sixteenth century says on this pas- \ 
sage : " They fall because every thing recurs to its na- i 
ture ; for if you throw a stone a thousand times into the j 
air, it will never accustom itself to move upwards.' i 
Perhaps we shall now find it difficult not to smile at the I 
idea we may form of this luckless experimentalist, teach- i 
ing stones to fly ; yet it may be useful to remember that I 
it is only because we have akeady collected an opinion : 
from the results of a vast number of observations in the I 
daily experience of life, that our ridicule would not be I 
altogether misplaced, and that we are totally unable to 
determine by any kind of reasoning, unaccompanied by 
experiment whether a stone throw^n into the air would 
fall again to the earth, or move for ever upwards, or in 
any other conceivable manner and direction. 


The opinion which Aristotle held, that motion must be 
caused by something in contact with the body moved, 
led him to his famous theory that falhng bodies are ac- 
celerated by the air through which they pass. We will 
show how it was attempted to explain this process when 
we come to speak of more modern authors. He classed 
natural bodies into heavy and light, remarking at the 
same time that it is cleai' that '' there are some bodies 
possessing neither gravity nor^ity.'^ By hght bodies, 
he understood those w^hich have a natural tendency to 
move from the earth, observing that '' that which is 
lighter is not always light." He maintained that the 
heavenly bodies were altogether devoid of gravity ; and 
we have already had occasion to mention his assertion 
that a large body falls faster than a small one in propor- 
tion to its weight. With this opinion may be classed 
another great mistake, in maintaining that the same bodies 
fall through different mediums, as air or water, with ve- 
locities reciprocally proportional to their denshies. By 
a singular inversion of experimental science. Cardan, re- 
lying on this assertion, proposed in the sixteenth century 
to determine the densities of air and water by observing 
the different times taken by a stone in falling through 
I them. Gahleo inquired afterw^ards why the experiment 
should not be made with a cork, which pertinent question 
put an end to the theory. 

There are curious traces still preserved in the poem of 
jLucretius of a mechanical philosophy, of which the credit 
is in general given lo Democritus, where many principles 
jare inculcated strongly at variance with Aristotle's no- 
tions. We find absolute levity denied, and not on- 
l|y the assertion that in a vacuum all things would fall,. 



but that they would fall with the same velocity ; and the 
inequalities which we observe are attributed to the right '1 
cause, the impediment of the air, although the error re- i 
mains of believing the velocity of bodies falling through 'i 
the air to be proportional to their weight.^ Such speci- ' 
mens of this earlier philosophy may well indispose us to- 
wards Aristotle, who was as successful in the science of ' 
motion as he was in astronomy in suppressing the knowl- ] 
— ■ — — ■ — — — .1 

* *' Nunc locus est, ut opinor, in his illud quoque rebus i 

Confirmare tibi, nuUam rem posse sua vi j 

Corpoream sursum ferri, sursumque meare. — i 
Nee quom subsiliunt ignes ad tecta doraorum, ^ 

Et celeri flamma degustant tigna trabeisque ^ 

Sponte sua facere id sine vi subicente putandum est. t 
— Nonne vides etiam quanta vi tigna trabeisque 
Respuat humor aquse 1 Nam quod magi' mersimus alturo 

Directa et magna vi multi pressimus segre : — 1 

Tarn cupide sursum revomit magis atque remittit ^ 

Plus ut parte foras emergant, exsiliant que : i 

— Nee tamen h^sc, quantu'st in sedubitamus, opinor, ^ 

Quinvacuum per inane deorsum cimcta ferantur, I 

Sic igitur debent flaramse quoque posse per auras i 

Aeris expressse sursum subsidere, quamquam I 

Pondera quantum in se est deorsum deducere pugnent. f 

— Quod si forte aliquis credit Graviora potesse M 

Corpora, quo cittius rectum per Inane feruntur^ ' {] 

— Avius a vera longe ratione recedit. I 
Nam per Aquas quaecunque cadunt atque Aera deorsum 
Hsec pro ponderibus casus celerare necesse'st 
Propterea quia corpus Aquse, naturaque tenuis 

Aeris baud possunt seque rem quamque morari : ' 
Sed citius cedunt Gravioribus exsuperata. 

At contra nulli de nulla parte, neque ullo ' 

Tempore Inane potest Vacuum subsistere reii j 
Quin, sua quod natura petit, considere pergat : 
Omnia qua propter debent per Inane quietum 

iEque ponderibus non sequis concita ferri." i 
De Rerum Natura, lib. ii, v. 184—239. \ 


edge of a theory so much sounder than that which he m> 
posed so long upon the credulity of his blinded admi- 

An agreeable contrast to Aristotle's mystical sayings 
and fruitless sylloVisms is presented in x^rchimedes' book 
on Equihbrium, in which he demonstrates very satisfac- 
torily, though with greater cunib^ousness of apparatus 
than is now thought necessary, the principal properties 
of the lever. This and the Treatise on the Equilibrium 
of Floating Bodies are the only mechanical works which 
have reached us of this writer, who was by common 
•consent one of the most accomplished mathematicians of 
antiquity. Ptolemy the astronomer wrote also a Treatise 
on Mechanics, now lost, which probably contained much 
that would be interesting in the history of mechanics ; 
for Pappus says, in the Preface to the Eighth Book of 
his Mathematical Collections : ''There is no occasion 
for me to explain what is meant by a heavy, and what by 
a hght body, and why bodies are carried up and down, 
and in what sense these very words ' up ' and ' down,' 
are to be taken, and by what limits they are bounded ; 
for all this is declared in Ptolemy's Mechanics." This 
book of Ptolemy's appears to have been also known by 
Eutocius, a commentator of Archimedes, who lived 
about the end of the fifth century of our era ; he intimates 
that the doctrines contained in it are grounded upon Aris- 
totle's ; if so, its loss is less to be lamented. Pappus' 
own book deserves attention for the enmperation which 
he makes of the mechanical powers, namely, the wheel 
and axle, the lever, pullies, the wedge and the screw. 
He gives the credit to Hero and Philo of having shown, 
j\ Hn works which have not reached us, that the theory of 


all these machines is the same. In Pappus we also find 
the first attempt to discover the force necessary to sup- 
port a given weight on an inchned plane. This in fact is 
involved in the theory of the screw ; and the same vicious 
reasoning which Pappus employs on this occasion w^as 
probably found in those treatises which he quotes with so 
much approbation. Numerous as are the faults of his 
pretended demonstration, it was received undoubtingly 
for a long period. 

The credit of first giving the true theory of equili- 
brium on the inclined plane is usually ascribed to Stevin, 
although, as we shall presently show, with very little rea- 
son. Stevin supposed a chain to be placed over two in- 
clined planes and to hang down in the manner represented 
in the figure. He then urged that ihe chain w^ould be in 
equilibrium ; for otherwise, it would incessantly continue 
in motion, if there w^ere any cause why it should begin to 
move. This being conceded, he remarks further, that 
the parts A D and B D are also in equilibrium, being ex- 
actly similar to each other ; and there- 
fore if they are taken away, the re- 
maining parts A C and B C will also 
j^^be in equilibrium. The weights of 
^ these parts are proportional to the 
^ ^ lengths A C and B C ; and hence Ste- 

%x^D o^' vin concluded that two weights would 
balance on two inclined planes, which 
are to each other as the lengths of the planes included 
between the same parallels to the horizon. This conclu- 
sion is the correct one, and there is certainly great 
ingenuity in this contrivance to facilitate the demon- 
str^ttion ; it must not however be mistaken for an 



a pri()ri proof, as it sometimes seems to have been : we 
should remember that the experiments which led to the 
principle of virtual velocities are also necessary to show 
the absurdity of supposing a perpetual motion, which is 
made the foundation of this theorem. That principle had 
been applied directly to determine the same proportion in 
a work written long before, where it has remained singu- 
larly concealed from the notice of most who have written 
on this subject. The book bears the name of Jordanus, 
who hved at Namur in the thirteenth century ; but Com- 
mandine, who refers to it in his Commentary on Pappus 
considers it as the work of an earlier period The au- 
thor takes the principle of virtual velocities for the ground- 
work of his explanations, both of the lever and inclined 
plane ; the latter will not occupy much space and in an 
historical point of view is too curious to be omitted. 

^'Qucest, 10. — If two weights descend by paths of 
different obliq]\ities, and the proportion be the same of 
the weights and^the inclinations be taken in the same or- 
der, they will have the same descending force. By the 
inclinations, I do not mean the angles, but the paths up to 
the point in which both meet the same perpendicular.* 

* This is not a literal translation, but by \vhat follows, is evidently the 
Author's meaning. His words are; '' Proportionem igitur declinationem 
dico non augulorum, sed linearum usque ad aequidistantem resecationem in 
q«a aequaliter supunt de directo." 


Let therefore, e be the weight upon d c, and h upon d a, 
and let e be to h rs d c to d a. I say these weights, in ^ 
this situation, are equally effective. Take d k equally*^ 
inclined with d c, and upon it a weight equal to e, which '^t 
call 6. If possible let e descend to /, so as to raise h to ^:. 
7?i, and take 6 n equal to /i m or e /, and draw the hori- ; 
zontal and perpendicular lines as in the figure. ' 

Then n z : n 6 : : d b : dk \ 

and m h : m X : :d a : d b ^ 

therefore n z : m x : : d a : d k : : /i : 6, and thei^efore ' 
since e r is not able to raise 6 to ?i, neither icill it be able \ 
to raise h to m ; therefore they will remain as they are.'' I 
The passage in Italics tacitly assumes the principle in j 
question. Tartalea, who edited Jordanus's book in 1565, j 
has copied this theorem verbatim into one of his own I 
treatises, and from that time it appears to have attracted 
no further attention. The rest of the book is of an in- ' 
ferior description. We find Aristotle's doctrine repeated \ 
that the velocity of a falhng body is proportional to its ' 
weight ; that the weight of a heavy body changes with its j 
form ; and other similar opinions. The manner in which | 
falling bodies are accelerated by the air is given in de- | 
tail. i 

^' By its first motion the heavy body will drag after it { 
what is behmd, and move what is just below^ it ; and these i 
when put in motion move what is next to them, so that i 
by being set in motion they less impede the falling body. ' 
In this manner it has the effect of being heavier, and im- ! 
pels still more those which give way before it, until at I 
last they are no lono-er impelled, but begin to drag. And 1 
thus it happens that its gravity is increased by their attrac- j 


tion, and their motion by its gravity, Avhence we see that 
its velocity is continually multiplied/' 

In this short review of the state of mechanical science 
before Galileo, the name of Guido Ubaldi ought not to 
be omitted, although his works contain Httle or nothing 
original. We have akeady mentioned Benedetti as 
having successfuDy attacked some of Aristotle's staVical 
doctrines, but it is to be noticed that the laws of motion 
were little if at all examined by any of these writers. 
There are a few theorems connected with this latter stib- 
ject in Cardan's extraordinary book '^ On Proportions,"^ 
but for the most part false and contradictory. In the 
sevent}^-first proposition of his fifth book, he examines the 
force of the screw^ in supporting a given weight, and de- 
termines it accm-ately on the principle of virtual reloci- 
ties ; namely, that the power applied at the end of the 
horizontal lever must make a complete circuit at that dis- 
tance from the centre, whilst the weight rises through the 
perpendicular height of the thread. The very next pro- 
position in the same page is to find the same relation be- 
tween the power and weight on an inclined plane ; and 
although the identity of principle in these two mechanical 
aids was well known, yet Cardan declares the necessary 
sustaining force to vary as the angle of inclination of 
the plane^ for no better reason than that such an expres- 
sion will properly represent it at the two limiting angles 
of inclination, since the force is nothing when the plane 
is horizontal, and equal to the weight when perpendi- 
cular. This again shows how cautious w^e should be 
in attributing the full knowledge of general principles to 
these early WTiters, on account of occasional indications 
of their having employed them. 



Galileo^ s theory of motion — Exti^acts from the Dialogues. 

During Galileo's residence at Sienna, when his recent 
persecution had rendered astronomy an ungrateful, and 
indeed an unsafe occupation for his ever active mind, he 
returned with increased pleasure to the favorite employ- 
ment of his earlier years, an inquiry into the laws and 
phenomena of motion. His manuscript treatises on mo- 
tion, written about 1590, which are mentioned by Ven- 
turi to be' in the Ducal library at Florence, seem, from 
the published titles of the chapters, to consist principally 
of objections to the theory of Aristotle ; a few only ap- 
pear to enter on a new field of speculation. The llthj 
13th, and 17th chapters relate to the motion of bodies 
on variously inclined planes, and of projectiles. The 
title of the 14th impHes a new theory of accelerated 
motion, and the assertion in that of the 16th, that a body 
falling naturally for however great a time wouid never ac- 
quire more than an assignable degree of velocity, shows 
that at this early period Galileo had formed just and ac- 
curate notions of the action of a resisting medium. It is 
hazardous to conjecture how much he might have then 
acquired of what we should now call more elementary 
knowledge ; a safer course w^ill be to trace his progress 
through existing documents in their chronological order. 
In 1602 we find Galileo apohgizing in a letter addressed 
to his early patron the Marchese Gbndo Ubaldi, for pres- 
sing again upon his attention the isoab-onism of the pen- 


dulum, which Ubaldi had rejected as false and impos- 
sible. It may not be superfluous to 'observe that Gali- 
leo's results are not quite accurate, for there is a percep- 
tible increase in the time occupied by the oscillations in 
larger arcs ; it is therefore probable that he was induced 
to speak so confidently of their perfect equality, from at- 
tributing the increase of time which he could not avoid 
remarking to the increased resistance of the air during 
the larger vibrations. The analytical methods then 
known would not permit him to discover the curious fact, 
that the time of a total vibration is not sensibly altered by 
this cause, except so far as it diminishes the extent of the 
swing, and thus in fact, (paradoxical as it may sound) 
renders each oscillation successively more rapid, though 
in a very small degree. He does indeed make the same 
remark, that the resistance of the air will not affect the 
time of the oscillation, but that assertion was a conse- 
quence of his erroneous behef that the time of vibration 
in all arcs is the same. Had he been aware of the varia- 
tion, there is no reason to think that he could have per- 
ceived that this result is not affected by it. In this letter 
is the first mention of the theorem, that the times of fall 
down all the chords drawn from the lowest point of a 
circle are equal ; and another, from which Gahleo after- 
wards deduced the curious result, that it takes less time 
to fall down the curve than down the chord, notwithstan- 
ding the latter is the direct and shortest course. In con- 
clusion he says, ''Up to this point I can go without ex- 
ceeding the limits of mechanics, but I have not yet been 
able to demonstrate that all arcs are passed in the same 
jtime which is what I am seeking. " In 1604 he addressed 


the following letter to Sarpi, suggesting the false theory 1 
sometimes called Baliani's, who took from Galileo. j 

^'Returning to the subject of motion, in which I waii \ 
entirely without a fixed principle, from which to deduce ) 
the phenomena I have observed, I have hit upon a pro- i 
position, which seems natural and likely enough ; and if? 
I take it for granted, I can show that the spaces passed ; 
in natural motion are in the double proportion of the j 
times, and consequently that the spaces passed in equal | 
times are as the odd numbers beginning from unity, and 
the rest. The principle is this, that the swiftness of the 
movable increases in the proportion of its distance 
from the point whence it began to move ; as for in- 
stance, — if a heavy body drop from A towards 
D, by the line A B C D, I suppose the degree 
of velocity which it has at B to bear to the ve- I 
locity at C the ratio of A B to A C. I shalj 
be very glad if your Reverence will consider i 
this, and tell me your opinidn of it. If we \ 
admit this principle, not only, as I have said, I 
shall we demonstrate the other conclusions? j 
but we have it in our power to show that ^ f 
body falling naturally, and another projected upwards, 
pass through the same degree of velocity. For if the 
projectile be cast up from D to A, it is clear that at D it 
has force enough to reach A, and no farther : and when 
it has reached C and B, it is equally clear that it is still 
joined to a degree of force capable of carrying it to A : 
thus it is manifest that the forces at D, C and B decrease in 
the proportion of A B, A C, and A D ; so that if, in fall- 
ing, the degrees of velocity observe the same proportion, 
that is true which I have hitherto maintained and believed. 




We have no means of knowing how early Galileo dis- 
covered the fallacy of this reasoning. In his Dialogues 
on Motion, which contain the correct theory, he has put 
this erroneous supposition in the mouth of Sagredo, on 
which Salviati remarks, ''Your discourse has so much 
likehhood in it, that our author himself did not deny to 
me when I proposed it to him, that he also had been for 
some time in the same mistake. But that which I after- 
wards extremely wondered at, was to see discovered in 
four plain words, not only the falsity, but the impossibili- 
ty of a supposition carrying with it so much of seeming 
truth, that although I proposed it to many, I never met 
with any one but did freely admit it to be so ; and yet it is 
as false and impossible as that motion is made in an instant : 
for if the velocities are as the spaces passed, those spaces 
will be passed in equal times, and consequently all motion 
must be instantaneous." The following manner of put- 
ting this reasoning will perhaps make the conclusion clear- 
er. The velocity at any point is the space that would be 
passed in the next moment of time, if the motion be suppos- 
ed to continue the same as at that point. At the beginning 
of the time, when the body is at rest, the motion is none ; 
and therefore, on this theory, the space passed in the next 
moment is none, and thus it will be seen that the body 
cannot begin to move according to the supposed law. 

A curious fact, noticed by Guido Grandi in his com- 
mentary on Galileo's Dialogues on Motion, is that this 
false law of acceleration is precisely that which would 
make a circular arc the shortest line of descent between 
two given points ; and although in general Galileo only 
declared that the fall down the arc is made in less time 
flian down the chord (in which he is quite correct) , yet in 


some places he seems to assert that the circular arc is 
absolutely the shortest line of descent, which is not true. 
It has been thought possible that the law, which on re- 
flection he perceived to be impossible, might have ori- 
ginally recommended itself to him from his perception 
that it satisfied his prejudice in this respect. 

John Bernouilli, one of the first mathematicians in 
Europe at the beginning of the last century, has given 
us a proof that such a reason might impose even on a 
strong understanding, in the following argument urged by 
him in favour of Galileo's second and correct theory, 
that the spaces vary as the squares of the times. He 
had been investiga^g the curve of swiftest descent, and 
found it to be a cyclVd, the same curve in which Huy- 
ghens had already proved that all oscillations are made in 
accurately equal times. '' I think it," says he, "worthy 
of remark that this identity only occurs on Galileo's sup- 
position, so that this alone might lead us to presume it to 
be the real law of nature. For nature, which always 
does everything in the very simplest manner, thus makes 
one line do double work, whereas on any other supposi- 
tion, we must have had two lines, one for equal oscilla- 
tions, the other for the shortest descent." 

Venturi mentions a letter addressed to Galileo in May 
1609, by Luca Valerio, thanking him for his experi-^ 
ments on the descent of bodies on inclined planes. His 
method of making these experiments is detailed in the Dia- 
logues on Motion : — ''In a rule, or rather plank of wood 
about twelve yards long, half a yard broad one way, and 
three inches the other, w^e made upon the narrow side or 
edge a groove of little more than an inch wide : we cut 
it very straight, and, to make it very smooth and sleek, . 


we glued upon it a piece of vellum, polished and smooth- 
ed as exactly as possible, and in that we let fall a very 
hard, round, and smooth brass ball, raising one of the 
ends of the plank a yard or two at pleasure above the 
horizontal plane. We observed, in the manner tliat I 
shall tell you presently, the time wliich it spent in running 
down, and repeated the same observation again and again 
to assure ourselves of the time, in which we never found 
any difference, no, not so much as the tenth part of one 
beat of the pulse. Having made and settled this experi- 
ment, we let the same ball descend through a fourth part 
only of the length of the groove, and found the measured 
time to be exactly half the former. Continuing our ex- 
periments with other portions of the length, comparing 
the fall through half, two-thirds, three-fourths, in short, 
with the fall through any part, we found by many hundred 
experiments that the spaces passed over w^ere as the 
squares of the times, and that this was the case in all in- 
clinations of the plank ; during which, we also remai^ked 
that the times of descent, on different inclinations, ob- 
serve accurately the proportion assigned to them farther 
on, and demonstrated by our author. As to the estima- 
tion of the time, we hung up a great bucket full of water, 
which by a veiy small hole pierced in the bottom squirted 
out a fine thread of water, which we caught in a small 
glass during the whole time of the different descents : 
then weighing from time to time, in an exact pair of scales, 
; the quantity of water caught in this way, the differences 
and proportions of their weights gave the differences and 
i proportions of the times ; and this with such exactness 
f that, as I said before, although the experiments were re- 
peated again and again, they never differed in any degree 


worth noticing." In order to get rid of the friction, 
Galileo afterwai'ds substituted experiments with the pen- \ 
dulum ; but with all his care he erred very widely in his | 
determination of the space through which a body would i 
fall in 1"^ if the resistance of the air and all other impe- j 
diments were removed. He fixed it at 4 braccia : : 
Mersenne has engraved the length of the 'braccia^ used 
by Galileo, in his ''^Harmonic Universelle," from which ; 
it appears to be about 23^ English inches, so that Gali- \ 
leo's result is rather less than eight feet. Mersenne's own | 
result from direct observation w^as thirteen feet : he also j 
made experiments in St. Peter's at Rome, with a pen- , 
dulum 325 feet long, the vibrations of which were made 
in 10'- ; from this the fall in 1' might have been deduced | 
rather more than sixteen feet, w^hich is very close to the ^ 
truth. ^ j 

From another letter also written in the eai^y part of \ 
1609, we learn that Galileo was then busied with exam- j 
ining the strength and resistance "^ of beams of different 
sizes and forms, and how much weaker they are in the | 
middle than at the ends, and how much greater weight j 
they can support laid along their whole length, than if : 
sustained on a single point, and of what form they should | 
be so as to be equally strong throughout." He was also '; 
speculating on the motion of projectiles, and had satis- ^ 
fied himself that their motion in a vertical direction is ■ 
unaffected by their horizontal velocity ; a conclusion : 
which combined with his other experiments, led him af- ! 
terwards to determine the path of a projectile in a non- i 
resisting medium to be parabolical. | 

Tartalea is supposed to have been the first to remark ] 
that no bullet moves in a horizontal line , but his theory | 


beyond this point was very erroneous, for he supposed the 
bullet's path through air to be made up of an ascending 
and descending straight line, connected in the middle by 
a circular arc. 

Thomas Digges, in his treatise on the Newe Science 
of Great Artillerie, came much nearer the truth ; for he 
remarked, that '' The bullet violentlye throwne out of 
the peece by the furie of the poulder hath two motions : 
the one violent, which endeuoreth to carry the bullet right 
out in his line diagonall, according to the direction of the 
peece's axis, from whence the violent motion proceed- 
€th ; the other naturall in the bullet itselfe, which endeuo- 
reth still to carrye the same directlye downeward by a 
right Hne perpendiculare to the horizon, and which dooth 
though insensiblye euen from the beginning by little and 
little drawe it from that direct and diagonall course." 
And a little farther he observes that ''These middle curve 
arkes of the bullet's circuite, compounded of the 
violent and naturall motions of the bullet, albeit they be 
indeed mere helicall, yet have they a very great resem- 
blance of the Arkes Conical. And in randons above 
45^ they doe much resemble the Hyperbole and in all 
vnder the Ellepsis. But exactly, they neuer accorde, 
being indeed Spirall mixte and Hehcall." 

Perhaps Digges deserves no greater credit from this 
latter passage than the praise of a sharp and accurate 
eye, for he does not appear to have founded this deter- 
mination of the form of the curve on any theory of the 
direct fall of bodies ; but Galileo's arrival at the same 
result was preceded, as we have seen, by a careful ex- 
amination of the simplest phenomena into which this com- 
pound motion may be resolved. But it is time to proceed 
to the analysis of his ''Dialogues on Motion," these pre*- 


liminary remarks on their subject matter having been 
merely intended to show how long before their publica- 
tion Galileo was in possession of the principal theories 
contained in them. 

Descartes, in one of his letters to Mersenne, insinu- 
ates that Galileo had taken many things in these Dialogues 
from him : the two which he especially instances are the 
isocnpnism of the pendulum, and the law of the spaces 
varying as the squares of the times. Descartes was 
born in 1596 : we have shown that Galileo observed the 
isochronism of the pendulum in 1583, and knew the law 
of the spaces in 1604, although he was then attempting 
to deduce it from an erroneous principle. As Descartes 
on more than one occasion has been made to usurp the 
credit due to Galileo, (in no instance more glaringly so 
than when he has been absurdly styled the forerunner of 
Newton,) it will not be misplaced to mention a few of 
his opinions on these subjects, recorded in his letters to 
Mersenne in the collection of his letters just cited : — ''I 
am astonished at what you tell me of having found by ex- 
periment that bodies thrown up in the air take neither 
more nor less time to rise than to fall again ; and you will 
excuse me if I say that I look upon the experiment as a 
very difficult one to make accurately. This proportion 
of increase according to the odd numbers 1, 3, 5, 7, &c. 
which is in Galileo, and which I think I wrote to you 
some time back, cannot be true, as I believe I intimated 
at the same time, jjple^s we make two or three supposi- 
tions which are entirely false. One is Galileo's opinion, . 
that motion increases gradually from the slowest degree ; / 
and the other is, that the air makes no resistance." In a 
later letter to the same person he says, apparently with 


some uneasiness, ''I have been revising nay notes on 
Galileo, in which I have not said expressly, that falling 
bodies do not pass through every degree of slowness, but 
I said that this cannot be determined w^ithout knowing 
what weight is ; which comes to the same thing. As to your 
example, I grant that it proves that every degree of veloc- 
ity is infinitely divisible, but not that a falling body actu- 
ally passes through all these divisions.— It is certain that 
a stone is not equally disposed to receive a new motion 
or increase of velocity, when it is already moving very 
quickly, and when it is moving slowly. But I believe 
that I am now able to determine in what proportion the 
velocity of a stone increases, not when falling in a va- 
cuum, but in this substantial atmosphere. — However I 
have now got my mind full of other things, and I cannot 
amuse myself with hunting this out, nor is it ci matter of 
much utility.'^'' He afterwards returns once more to the 
same subject : — ''As to w^hat Galileo says, that falling 
bodies pass through every degree of velDcity, I do not 
beheve that it generally happens, but I allow it is not im- 
possible that it may happen occasionally." After this 
the reader will know what va^ue to attach to the follow^- 
ing assertion by the same Descartes : — "I see nothing in 
Galileo's books to envy him and hardly any thing which 
I would own as mine;" and then may judge how far 
Salusbury's blunt declaration is borne out, ''Where or 
when did any one appear that durst enter the list with 
our Galileus ? save only one bold and .fortunate French- 
man, who yet no sooner came wifiih .he ring but he was 
hissed out again." 

The principal merit of Descartes must undoubtedly 
be derived from the great advances he made in what are 

W 2 


generally termed Abstract or Pure Mathematics ; nor 
was he slow to point out to Mersenne and his other 
friends the acknowledged inferiority of Galileo to him- 
self in this respect. We have not sufficient proof that this 
difference would have existed if Galileo's attention had 
been equally directed to that object ; the singular ele- 
gance of some of his geometrical constructions indicates 
great talent for this as well as for his own more favorite 
speculations. But he was far more profitably employed : 
geometry and pure mathematics already far out-stripped 
any useful application of their results to physical science, 
and it was the business of Gahleo's hfe to bring up 
the latter to the same level. He found abstract the- 
orems already demonstrated in sufficient number for 
his purpose, nor was there occasion to task his genius 
in search of new methods of inquiry, till all was ex- 
hausted which could be learned from those already in 
use. The result of his labors was that in the age im- 
mediately succeeding Galileo, the study of nature was 
no longer in arrear of the abstract theories of number 
and measure ; and when the genius of Newton pressed 
it forward to a still higher degree of perfection, it be- 
came necessary to discover at the same time more 
powerful instruments of investigation. This alternating 
process has been successfully continued to the present 
time ; the analyst acts as the pioneer of the naturalist, 
so that the abstract researches, which at first have no 
value but in the eyes of those to whom an elegant for- 
mula, in its own beauty, is a source of pleasure as real 
and as refined as a painting or a statue, are often found 
to furnish the only means for penetrating into the most 
intricate and concealed phenomena of natural philo- 


Descartes and Delambre agree in suspecting that 
Galileo preferred the dialogistic form for his treatises, 
because it afforded a ready oportunity for him to praise 
his own inventions : the reason which he himself gave 
is, the greater facihty for introducing new matter and 
collateral inquiries, such as he seldom failed to add each 
time that he repwused his work. We shall select in 
the first place enough to show the extent of his knowl- 
edge on the principal subject, motion, and shall then 
allude as well as our hmits will allow to the various 
other points incidentally brought forward. 

The dialogues are between the same speakers as in 
the " System of the world ;" and in the first, Simplicio 
gives Aristotle's proof, that motion in a vacuum is 
impossible, because according to him bodies move with' 
velocities in the compound proportion of their weight 
and the rarities of the mediums through which they 
move. And since the density of a vacuum bears no 
assignable ratio to that of any medium in which motion 
has been observed, any body which should employ time 
in moving through the latter, would pass through the 
same distance in a vacuum instantaneously, which is im- 
possible. Salviati replies by denying the axioms, and 
asserts that if a cannon ball weighing 200 lbs., and a 
musket ball w^eighing half a pound, be dropped together 
from a tower 200 yards high, the former will not an- 
ticipate the latter by so much as a foot ; '' and I 
would not have you do as some are wont, who fasten 
upon some saying of mine that may want a hair's breadth 
of the truth, and under this hair they seek to hide another 
man's blunder as big as a cable. Aristode says that an 
iron ball weighing 100 lbs. will fall from the height of 


100 yards while the weight of one pound falls but one 
yard : I say they will reach the ground together. They 
find the bigger to anticipate the less by two inches, and 
under these two inches they seek to hide Aristotle's 99 
yards." In the course of his reply to this argument 
Salviati formally announces the principle which is the 
foundation of the whole of Galileo's theory of motion, 
and which must therefore be quoted in his own words : 
- — '' A heavy body has by nature an intrinsic principle 
of moving towards the common centre of heavy things ; 
that is to say, to the centre of our terrestrial globe, with 
a motion continually accelerated in such manner that 
in equal times there are always equal additions of velo- 
city. This is to be understood as holding true only 
when all accidental and external impediments are 
removed, amongst which is one that we cannot obviate, 
namely, the resistance of the medium. This opposes 
itself, less or more, accordingly as it is to open more 
slowly or hastily to make way for the movable, which 
being by its own nature, as I have said, continually 
accelerated, consequently encounters a continually in- 
creasing resistance in the medium, until at last the velocity 
reaches that degree, and the resistance that power, 
that they balance each other ; all further acceleration 
is prevented, and the movable continues ever after 
with an uniform and equable motion." That such limi- 
ting velocity is not greater than some which may be 
exhibited may be proved as Galileo suggested, by 
firing a bullet upwards, which will in its descent strike 
the ground with less force than it would have done i 
immediately from the mouth of the gun; for he arguec 
that the degree of velocity which the air's resistance k i 


capable of diminishing must be greater than that which 
could ever be reached by a body falling naturally from 
rest. '' I do not think the present occasion a fit one 
for examining the cause of this acceleration of natural 
motion, on which the opinions of philosophers are much 
divided ; some referring it to the approach towards the 
centre, some to the continual diminution of that part 
of the medium remaining to be divided, some to a certain 
extrusion of the amliitent medium, which uniting again 
behind the movable, presses and hurries it forwards. 
All these fancies, with others of the hke sort, we might 
spend our time in examining, and with httle to gain by 
resolving them. It is enough for our author at present 
that we understand his object to be, the investigation 
and examination of some phenomena of a motion so ac- 
celerated, (no matter what may be the cause,) that the 
momenta of velocity, from the beginning to move from 
rest, increase in the simple proportion in which the time 
increases, which is as much as to say, that in equal 
times are equal additions of velocity. And if it shall 
turn out that the phenomena demonstrated on this sup- 
position ai'e verified in the motion of falhng and naturally 
accelerated weights, we may thence conclude that the 
assumed definition does describe the motion of heavy 
bodies, and that it is true that their acceleration varies 
in the ratio of the time of motion," 

When Gahleo first published these Dialogues on 
Motion, he was obliged to rest his demonstrations upon 
another principle besides, namely, that the velocity ac- 
i quired in falling down all incHned planes of the same 
perpendicular height is the same. As this result was 
derived directly from experiment, and from that only 



his theory was so far imperfect till he could show its 
consistency with the above supposed law of acceleration . 
When Viviani was studying with Galileo, he expressed 
his dissatisfaction at this chasm in the reasoning ; the 
consequence of which was, that Galileo, as he lay the 
same night, sleepless through indisposition, discovered 
the proof which he had long sought in vain, and intro- 
duced it into the subsequent editions. The third dia- 
logue is principally taken up with theorems on the direct 
fall of bodies, their times of descent down differently 
inclined planes, which in planes of the same height he 
determined to be as the lengths, and with other inquiries 
connected with the same subject, such as the straight 
lines of shortest descent under different data, &c. 

The fourth dialogue is appropriated to projectile motion, 
determined upon the principle that the horizontal motion 
will continue the same as if there w^ere no vertical mo- 
tion, and the vertical motion as if there were no horizon- 

Til n C B JL 








tal motion. "^^ A B represent a horizontal line or plane 
placed on high, on which let a body be carried with an^ 
equable motion from A towards B, and the support of. 
the plane being taken away at B, let the natural motion, 
downwards due to the body's weight come upon it in j 

Life of GALILEO, SQ2 

the direction of the perpendicular B N. Moreover let 
the straight Hne B E draw in the direction A B be taken 
to represent the flow, or measure, of the time, on which 
let any number of equal parts B C, C D, D E, &c. 
be marked at pleasure, and from the points C, D, E 
let Hues be drawn parallel to B N ; in the first of these 
let any part C I be taken, and let D F be taken four 
times as great as C I, E H nine times as great, and so 
on, proportionally lo the squares of the lines B C, B D 
B E, &c. or, as we say, in the double proportion of 
these lines. Now if we suppose that whilst by its equa- 
ble horizontal motion the body moves from B to C 
it also descends by its weight through C I, at the end 
of the time denoted by B C it will be at I. Moreover in 
the time B D, double of B C, it will have fallen four 
times as far, for in the first part of the treatise it has 
been shewn that the spaces fallen through by a heavy 
body vary as the squares of the times. Similarly at 
the end of the time B E, or three times B C, it will 
have fallen through E H, and will be at H. And it is 
plain that the points I, F, H, are in the same parabolical 
hne B I F H. The same demonstration will apply 
if we take any number of equal particles of time of what- 
I ever duration.'' 

The curve called here a Parabola by Galileo, is one 
of those which results from cutting straight through a 
1 Cone, and therefore is called also one of the Clonic 
j Sections the curious properties of which curves had 
' drawn the attention of geometricians long before Galileo 
j thus began to point out their intimate connexion with the 
phenomena of motion. After the proposition we have 
I just extracted, he proceeds to anticipate some objections 


to the theory, and explains that the course of a projec- 
tile will not be accurately a parabola for two reasons ; 
partly on account of the resistance of the air, and partly 
because a horizontal line, or one equi-distant from the 
earth's centre, is not straight, but circular. The latter 
cause of difference will however, as he says, be insensible 
in all such experiments as we are able to make. The 
rest of the Dialogue is taken up with different construc- 
tions for determining the circumstances of the motion 
of projectiles, as their range, greatest height, &c. ; and 
it is proved that, with a given force of projection, the 
range will be greatest when a ball is projected at an 
elevation of 45^, the ranges of all angles equaly inchned 
above and below 4"3o corresponding exactly to each 

One of the most interesting subjects discussed in 
these Dialogues is the famous notion of nature's horror 
of a vacuum or empty space, which the old school of 
philosophy considered as impossible to be obtained. Gali- 
leo's notions of it were very different ; for although he 
still unadvisedly adhered to the old phrase to denote the 
resistance experienced in endeavoring to separate two 
smooth surfaces, he was so far from looking upon a 
vacuum as an impossibihty, that he has described an 
apparatus by which he endeavors to measure the force 
necessary to produce one. This consisted of a cylinder, 
into which is tightly fitted a piston ; through 
the centre of the piston passes a rod with a 
I conical valve, which, when drawn down, 
shuts the aperture closely, supporting a bas- 
ket. The space between the piston and 
cylinder being filled full of water poured in 


through the aperture, the valve is closed, the vessel 
reversed, and weights are added till the piston is drawn 
forcibly downwards. Gahleo concluded that the weight 
of the piston, rod, and added weights, would be the 
measure of the force of resistance to the vacuum which 
he supposed would take place between the piston and 
lower surface of the water. The defects in this appara- 
tus for the purpose intended are of no consequence, so 
far as regards the present argument, and it is perhaps 
needless to observe that he was mistaken in supposing 
the water w^ould not descend with a piston. This ex- 
periment occasions a remark from Sagredo, that he 
had observed that a lifting-pump would not work when 
the water in the cistern had sunk to the depth of thirty- 
five feet below the valve ; that he thought the pump was 
injured, and sent for the maker of it, w^ho assured him 
that no pump upon that construction w^ould lift water 
from so great a depth. This story is sometimes told of 
Galileo, as if he had said sneeringly on this occasion that 
Nature's horror of a vacuum does not extend beyond 
thirty-five feet ; but it is very plain that if he had made 
such an observation, it would have been seriously ; and 
in fact by such a limitation he deprived the notion of 
the principal part of its absurdity. He evidently had 
adopted the common notion of suction, for he compares 
the column of w^ater to a rod of metal suspended from 
its upper end, which may be lengthened till it breaks 
with its own w^eight. It is certainly very extraordinary 
that he failed to observe how simply this phenomena 
may be explained by a reference to the weight of the 
elastic atmosphere, w-hich he w^as perfectly well ac- 
quainted with, and endeavored by the following ingen- 




ious experiment to determine: — ''Take a large glass i 

flask with a bent neck, and round its mouth tie a lean;j- ' 

ern pipe with a valve in it, through which water ma^ \ 
be forced into the flask with a syringe without suffering 

any air to escape, so that it will be 'compressed within i 

the bottle. It will be found difficult to force in more ! 
than about three-fourths of what the flask will hold, 

which must be carefully weighed. The valve must ; 

then be opened, and just so much air will rush out as ^ 

would in its natural density occupy the space now filled | 

by the water. Weigh the vessel again ; the difference I 

will show the weight of that quantity of air^." By , 

these means, which the modern experimentalist will see i 
were scarcely capable of much accuracy, Galileo found 

that air was four hundred times Hghter than water, in- ; 

stead of ten times, which was the proportion fixed on | 

by Aristotle. The real proportion is about 830 time-s. | 

The true theory of the rise of water in a lifting-pump | 

is commonly dated from TorriceUi's famous experiment ' 

with a Qolomn of mercury, in 1644, when he found that ' 

the greatest height at which it would stand is fourteen I 

times less than the height at which water will stand, ^ 

which is exactly the proportion of weight between water | 

and mercury. The following curious letter from Bali- | 

ani, 1630, shows that the original merit of suggesting j 

the real cause belongs to him, and renders it still more | 

unaccountable that Galileo, to whom it > was addressed, I 
should not at once have adopted the same view of the 

subject: — ''I have believed that a vacuum may exist || 

naturally ever since I knew that the air has sensible :: 

* It has been recently proposed to determine the density of high-pressure 
steam by a process analogous to this. 


weight, and that you taught me in one of your letters 
how to find its weight exactly, though I have not yet 
succeeded with that experiment. From that moment 
i took up the notion that it is not repugnant to the na- 
ture of things that there should be a vacuum, but mere- 
ly that it is difficult to produce. To explain myself 
more clearly : if we allow that the ai» has weight, there 
is no difference between air and water except in degree. 
At the bottom of the sea the weight of the water above 
me compresses everything around my body, and it 
strikes me that the same thing must happen in the air, 
we being placed at the bottom of its immensity ; we do 
not feel its weight, nor the compression round us, be- 
cause our bodies are made capable of supporting it. 
But if we were in a vacuum, then the weight of the air 
above our heads would be felt. It would be felt very great, 
but not infinite, and therefore deterininable, and it might 
be overcome by a force proportioned to it. In fact I 
estimate it to be such that, to make a vacuum, I believe 
we require a force greater than that of a column of WE' 
ter thirty feet high." 

This subject is introduced by some observations on th6 
force of cohesion, Galileo seeming to be of opinion that, 
although it cannot be adequately accounted for by the 
^' great and principal resistance to a vacuum, yet that 
perhaps a sufficient cause may be found by considering 
every body as composed of very minute particles, be- 
tween every two of which is exerted a similar resistance. " 
This remark serves to lead to a discussion on indivisi- 
bles and infinite quantities, of which we shall merely ex- 
tract what Galileo gives as a curious paradox suggested 
in the course of it. He supposes a basin to be formed 


by scooping a hemisphere out. of a cylinder, and a cone 
to be taken of the same depth and base as the hemisphere. 
It is easy to show, if the cone and scooped cyhnder be 
both supposed to be cut by the same plane, parallel to 
the one on which both stand, that the area of the ririp; 

C D E F thus discovered in the cylinder is equal to the ' 

area of the corresponding circular section A B of the : 

cone wherever the cutting plane is supposed to be.^ • 

He then proceeds with these remarkable words : — ^ ' If 

we raise the plane higher and higher, one of these areas ; 

terminates in the circumference of a circle, and the other ; 

in a point, for such are the upper rim of the basin and the j 

tpp of the cone. Now since in the diminution of the twa , 

areas they to the very last maintain their equality to one ; 

another, it is in my thoughts proper to say that the high- ! 

est and ultimate terms of such dimmutions are equau 1 

and not one infinitely bigger than the other. It seems I 

therefore that the circumference of a large circle may be i 

said to be equal to one single point. And why may | 

not these be called equal if they be the last remainders | 

and vestiges left by equal magnitudes ?" i 

We think no one can refuse to admit the probability, 
that Newton may have found in such passages as these 

the first germ of the idea of his prime and ultimate ratios, ; 

which afterwards became in his hands an instrument of < 

* Galileo also reasons in the same way on the equality of the solids stand- ] 
ing on the cutting plane, but one is sufficient for our present purpose, ! 


such power. As to the paradoxical result, Descartes 
undoubtedly has given the true answer to it in saying that 
it only proves that the hne is not a greater area than 
the point is. Whilst on this subject, it may not be un- 
interesting to r/etiiark that something similar to the doc- 
trine of flummis seems to have been lying dormant in 
the minds of the mathematicians of Galileo's era, for 
Inchoffer illustrates his argument in the treatise we have 
already mentioned, that the Copernicans may deduce 
some true results from what he terms their absurd hy- 
pothesis, by observing, that mathematicians may deduce 
the truth that a line is length without breadth, from the 
false and physically impossible supposition that a point 
flow^s, and that a line is the fluxion of a point. 

A suggestion that perhaps fire dissolves bodies by in- 
sinuating itself between their minute particles, brings on 
the subject of the violent effects of heat and light ; on 
which Sagredo inquires, whether we are to take for 
granted that the effect of light does or does not require 
time. Simplicio is ready with an answer, that the dis- 
charge of artillery proves the transmission of light to be 
instantaneous, to which Sagredo cautiously replies, that 
nothing can be gathered from that experiment except that 
light travels more swiftly than sound ; nor can we draw 
any decisive conclusion from the rising of the sun. 
*'^Who can asbure us that he is not in the horizon be- 
fore his rays reach our sight ?" Salviati then mentions 
an experiment by which he endeavored to examine this 
question. Two observers are each to be furnished with 
a lantern : as soon as the first shades his light, the sec- 
ond is to discover his, and this is to be repeated at a 
short distance till the observers are perfect in th^ pra.c- 


tice. The same thing is to be tried at the distance of i 

several miles, and if the first observer perceive any | 

delay between shading his own hght and the appearance i 
of his companion's, it is to be attributed to the time 
taken by the light in traversing twice the distance be- 
tween them. He allows .that he could discover no 
perceptible interval at the distance of a rhile, at which 

he had tried the experiment, but recommends that with ; 

the help of a telescope it should be tried at much great- ; 

er distances. Sir Kenelm Digby remarks on this pas- | 

sage : '' It may be objected (if there be some observa- I 

ble tardity in the motion of light) that the sunne would j 

never be truely in that place in which unto our eyes | 

he appeareth to be ; because that it being scene by j 

means of the light which issueth from it, if that light ; 

be required time to move in, the sunne (whose motion | 

is so swifte) would be removed from the place where j 

the light left it, before it could be with us to give ti- j 

dings of him. To this I answer, allowing perai^^enture f 

tliat it may be so, who knoweth the contrary ? Or t 

what inconvenience would follow if it be admitted ?" -i 

The principle thing remaining to be noticed is the 

application of the theory of the pendulum to musical ' 

concords and dissoij^ces, which are explained, in the ; 

same manner as by Kepler in His '^ Harmonices Mundi," j 

to result from the concurrence or opposition of vibra-* j 

tions in the air striking upon the drum of the ear. It f 

is suggested that these vibrations may be made manifest I 

by rubbing the finger round a glass set in a large vessel i 
of water; ''and if by pressure the note is suddenly 
made to rise to the octave above, every one of the 
undulations w^hich will be seen regularly spreading round 


the glass, will suddenly split into two, preying that the 
vibrations that occasion the octave are double those be- 
longing to the simple note." Galileo then describes a 
method he discovered by accident of measuring the 
length of these waves more accurately than can be done 
in the aghated water. He was scraping a brass plate with 
an iron chisel, to take out some spots, and moving the 
tool rapidly upon the plate, he occasionally heard a his- 
sing and whisthng sound, very shrill and audible, and 
whenever this occurred, and then only, he observed the 
hght dust on the plate to arrange itself in a long row of 
small parallel streaks equidistant from each other. In 
repeated experiments he produced different tones by 
scraping with greater or less velocity, and remarked 
that the streaks produced by the acute sounds stood clos- 
er together than those from the low notes. Among the 
sounds produced were two, which by comparison with 
a viol he ascertained to differ by an exact fifth : and 
measuring the spaces occupied by the streaks in both 
experiments, he found thirty of the one equal to forty- 
five of the other, which is exactly the known proportion 
of the length of the strings of the same material which 
sound a fifth to each other^. 

Salviati also remarks, that if the material be not the 
?ame, as for instance if k be required to sound an oc- 
tave to a note on catg^, on a wire of the same length, 
the weight of the wire must be made four times as 
great, and so for other intervals. ''The immediate 
cause of the forms of musical intervals is neither the 

* This beautiful experiment is raore easily tried by drawing the bow ol 
a violin across the edge of a glass strewed with fine diy saod. Those who 
wish to see more on the subject may consult Chladni's * Acoustique.' 


length, the tension, nor the thickness, but the propor- 
tion of the numbers of the undulations of the air which 
strike upon the drum of the ear, and make it vibrate 
in die same intervals. Hence we may gather a- plaus- 
ible reason of the different sensations occasioned to us 
by different couples of sounds, of which we hear some 
w^ith great pleasure, some with less, and call ihem ac- 
cordingly concords, more or less perfect, wdiilst some 
excite in us great dissatisfaction, and are called discords. 
The disagreeable sensation belonging to the latter prob- 
ably arises from the disorderly manner in which the 
vibrations strike the drum of the ear ; so that for in- 
stance a most cruel discord would be produced by 
sounding . together two strings, of which the lengths are 
to each other as the side and diagonal of the square ^ 
which is the discord of ihe false fifth. On the contrary, 
agreeable consonances w^hich result from the strings of 
which the number of the vibrations made in the same 
time are commensurable, ''to the end that the cartilage 
of the drum may not undergo the incessant torture of a 
double inflexion from the disagreeing percussions." 
Something similar may be exhibited to the eye by hang- 
ing up pendulums of different lengths: ''if these be 
proportioned so that tlie times of their vibrations cor- 
respond with those of the musical concords, the eye 
will observe with pleasure their crossings and interweav- 
ings still recurring at appreciable intervals ; but if the 
times of vibration be incomnj^nsurate, the eye will be 
wearied and worn out with following them," 

The second dialogue is occupied entirely with an in- 
vestigation of the strength of beams, a subject which does 
not appear to have been examined by any one before 


Galileo beyond Aristotle's remark, that loog beams are 
weaker, because they are at once the weight, the lever, 
and the fulcrum ; and it is in the development of this 
observation that the whole theory consists. The princi- 
ple assumed by Galileo as the basis of his inquiries is, 
that the force of cohesion with which a beam resists a 
cross fracture in any section may all be considered as ac- 
ting at ilie centre of gravity of the section, and that it 
breaks always at the lowest point : from this he deduced 
that the effect of the weight of a prismatic beam in over- 
coming the resistance of one end by which it is fastened 
to a wall, varies directly as the square of the length, and 
inversally as the side of the base. From this it immedi- 
ately follows, tliat if for instance the bone of a large ani- 
mal be three times as long as the corresponding one in a 
smaller beast, it must be nine times as thick to have the 
same strength, provided we suppose inboth cases that the 
materials are of the same consistence. An elegant result 
vvhich Galileo also deduced from this theory, is that the 
form of such a beam, to be eoually strong in every part, 
should be that of a parabolical prism, the verta^ ot tne 
parabola being the farthest removed from th^vall. As 
an easy mode of describing the parabolic curve for this 
purpose, he recommends tracing the line in w^hich a hea^y 
flexible strmg hangs. This curve is not an accurate par* 
abola : it is now called a ca^^ary ; but it is plain from 
the description of it in the fourth dialogue, that Galileo 
was perfectly aware that this construction is only approx- 
imately true. In the same place he makes the remark, 
which to m.any is so paradoxical, that no force, however 
great, exerted in a horizontal direction, can stretch a heavy 
thread, however slender, into an accurately strai2;ht line. 


The fifth and sixth dialogues were left unfinished, and 
annexed to the former ones by Viviani after Galileo's 
death : the fragment of the fifth, which is on the subject 
of Euclid's definition of Ratio, was at first intended to 
have formed a part of the third, and followed the first pro- 
position on equable motion : the sixth was intended to 
have embodied Galileo's researches on the nature and laws 
of percussion, on which he was employed at the time 
of his death. Considering these solely as fragments, we 
shall not h«re make any extracts from them. 


Correspondence on Longitudes. — Pendulum Clock» 

In the spring of 1636, having finished his Dialogues on 
Motion, Galileo resumacd the plan of determining the 
longitude by means of Jupiter's satellites. Perhaps he 
suspected something of the private intrigue which thwart- 
ed his former expectations from the Spanish Government, 
and this may have induced him on the present occasion 
to negotiate the matter without applying for Ferdinand's 
assistance and recommendation. Accordingly he ad- 
dressed himself to Lorenz Real, who had been Govern- 
or General of the Dutch possesions in India, freely and 
unconditionally offering the use of his theory to the State.^j 
General of Holland. Not long before, his opinion had 


been requested by the commissioners appointed at Paris 
to examine and report on the practicability of another 
method proposed by Morin, which consisted in observing 
the distance of the moon from a known star. Morin w^as 
a French philosopher, principally known as an astrologer 
and zealous iVnti-Copernican ; but his name deserves to 
be recorded as undoubtedly one of the first to recommend 
a method, which, under the name of a Lunar distance, 
is now in universal practice. 

The monthly motion of the moon is so rapid, that her 
distance from a given star sensibly varies in a few min- 
utes even to the unassisted eye ; and with the aid of the 
telescope, we can of course appreciate the change more 
accurately. Morin proposed that the distances of the 
moon from a number of fixed stars lying near her path 
in the heavens should be beforehand calculated and reg- 
istered for every day in the year, at a certain hour, in the 
place from which the longitudes were to be reckoned, as 
for instance at Paris : just as in the case of the eclipses 
of Jupiter's satellites, the observer, when he saw that the 
moon had arrived at the registered distance, would know 
the hour at Paris : he might also make allowance for in- 
termediate distances. Observing at the same instant the 
hour on board his ship, the difference between the two 
would show his position in regard of longitude. In using 
this method as it is now practised, several modifications 
are to be attended to, without which it would be wholly 
useless, in consequence of the refraction of the atmos- 
phere, and the proximity of the moon to the earth. 
Owing to the latter cause, if two spectators should at the 
same instant of time, but in different places, measure the 
distance of the moon in the East, from a star still more 


to the eastward, it would appear greater to the more east- 
erly spectator than to the other observer, who as seen 
from the star would be standing more directly behind the 
moon. The mode of allowing for these alterations is 
taught by trigonometry and astronomy. 

The success of this method depends altogether upon 
the exact knowledge which w^e have of the moon's course, 
and till that knowledge w^as perfected it would have been 
found altogether illusory. Such in fact was the judgment 
which Galileo pronounced upon it, ''As to Morin's 
book on the method of finding the longitude by means of . 
the moon's motion, I say freely that I conceive this idea 
to be as accurate in theory, as fallacious and impossible 
in practice. I am sure that neither you nor any one of 
the other four gentlemen can doubt the possibihty of 
finding the difference of longitude between two meridi- 
ans by means of the moon's motion, provided we are sure 
of the following requisites : First, an Ephemeris of the 
moon's motion exactly calculated for the first meridian 
from which the others are to be reckoned ; secondly ^ ex- 
act instruments, and convenient to handle, in taking the 
distance between the moon and a fixed star ; thirdly, 
great practical skill in the observer ; fourthly, not less 
accuracy, in the scientific calculations, and astronomical 
computations ; fifthly, very perfect clocks to number the 
hours, or other means of knowing them exactly, &c* 
Supposing, I say, all these elements free from error, the 
longitude will be accurately found ; but I reckon it more 
easy and likely to err in all of these together, than to be i 
practically right in one alone. Morin ought to require his j 
judges to assign, at their pleasure, eight or ten moments of 
different nights dming four or six months to come, and , 


pledge himself to predict and assign by his calculations the 
distances of the moon at those determined instants from 
some star which would then be near to her. If it is 
found that the dktances assigned by him agree with those 
which the quaint or ^se:5^nt* will actually show, the 
judges would be satisfied of his success, or rather of 
the truth of the matter, and nothing would remain but to 
show that his operations were such as could be perform- 
ed by men of moderate skill, and also practicable at sea 
as well as on land. I incline much to think that an ex- 
periment of this kind would do much towards abating the 
opinion and conceit which Morin has of himself, which 
appears to me so lofty, that I should consider myself the 
eighth sage, if I knew the half of what Morin presumes to 

It is probable that Galileo was biassed by a predilec- 
tion for his own method, on which he had expended so 
much time and labor ; but the objections which he raises 
against Morin's proposal in the foregoing letter are no 
other than those to which at that period it was undoubt- 
edly open. With regard to his own, he had aheady, in 
I 1612, given a rough prediction of the course of Jupiter's 
j satelHtes, which had been found to agree tolerably well 
' with subsequent observations ; and since that time, amid 
all his other employments, he had almost unintermit- 
tingly during twenty-four years contmued his observa- 
I tions, for the sake of bringing the tables of their motions 
to as high a state of perfection as possible. This was 
the point to which the inquiries of the States in their an- 
swer to Galileo's frank proposal were principally direct- 

f These instruments were very inferior to those now in use under the same 


ed. They immediately appointed commissioners to 
communicate with him, and report the various points on 
which they required information. They also sent him a 
golden chain, and assured him that in the case of the de- 
sign proving successful, he should have no cause to 
complain of their want of gratitude and generosity. The 
commissioners immediately commenced an active corres- 
pondence with him, in the course of which he entered 
into more minute details with regard to the methods by 
which he proposed to obviate the practical difficulties of 
the necessary observations. 

It is w^orth noticing that the secretary to the Prince of 
Orange, who was mainly instrumental in forming this 
commission, was Constantino Huyghens, father of the cele- 
brated mathematician of that name, of whom it has been 
said that he seemed destined to complete the discoveries 
of Galileo ; and it is not a little remarkable, that Huy- 
ghens nowhere in his published works makes any allu- 
sion to this connexion between his father and Galileo, 
not even during the discussion that arose some years 
later on the subject of the pendulum clock, which must 
necessarily have forced it upon his recollection. 

The Dutch commissioners had chosen one of their 
number to go into Italy for the purpose of communicat- 
ing personally with Galileo, but he discouraged this 
scheme, from a fear of its giving umbrage at Rome. The 
correspondence being carried on at so great a distance 
necessarily experienced many tedious delays, till in the 
very midst of Galileo's labors to complete his tables, he 
was seized with the blindness w^hich we have abeady 
mentioned. He then resolved to place all the papers 
containing his observations and calculations for this pur- 


pose in the hands of Renieri, a former pupil of his, and 
then professor of mathematics at Pisa, who undertook to 
finish and to forward them into Holland. Before this 
was done a new delay was occasioned by the deaths 
which speedily followed each other of every one of the 
four commissioners ; and for two or three years the cor- 
respondence with Holland was entirely interrupted. 
Constantino Huyghens, who was capable of appreciating 
the value of the scheme, succeeded after some trouble in 
renewing it, but only just before the death of Galileo 
himself, by which of com^se it was a second time broken 
off ; and to complete the singular series of obstacles by 
which the trial of this method was impeded, just as Re- 
nieri, by order oSp the Duke of Tuscany, was about to 
publish the ephemeris and tables which Galileo had en- 
trusted to him, and which the Duke told Viviani he had 
seen In flis possession, he also was attacked with a mor- 
tal malady ; and upon his death die manuscripts were 
nowhere to be found, nor has it since been discovered 
what became of them. Montucla has intimated his sus- 
picions that Renieri himself destroyed them, firom a con- 
sciousness tliat they were insufficient for the purpose to 
which it was intended to apply them ; a bold conjecture 5 
and one which ought to rest upon something more than 
mere surmise : for although it may be considered certain^ 
that the practical value of these tables would be very in- 
considerable in the present advanced state of knowledge, 
yet it is nearly as sure that they were unique at that time, 
and Renieri was aware of the value which Galileo him- 
self had set upon them, and should not be Hghtly accused 
of betraying his trust in so gross a manner. In 1665, 
BoreUi calculated the places of the satellites for every 


day in the ensuing year, which he professed to have de- 
duced (by desire of the Grand Duke) from Galileo's ta- 
bles ; but he does not say whether or not these tables 
were the same that had been in Renieri's possession. 

We have delayed till this opportunity to examine how 
far the invention of the pendulum clock belongs to GaH- 
leo. It has been asserted that the isod^r^ism of the 
pendulum had been noticed by Leonardo da Vinci, but 
the passage on which this assertion is founded (as trans- 
lated from his manuscripts by Venturi) scarcely warrants 
this conclusion. '' A rod which engages itself in the op- 
posite teeth of a spur-wheel can act like the arm of the 
balance in clocks, that is to say, it will act alternately, 
first on one side of the wheel, then on the opposite one, 
without interruption." If Da Vinci had constructed a 
€lock on this principle, and recognized the superiority of 
the pendulum over the old balance, he would surely have 
done more than to mention it as affording an unintermit- 
ted motion '' like the arm of the balance." The use of 
the balance is supposed to have been introduced at least 
as early as the fourteenth century. Venturi mentions 
the drawing and description of a ^-clock in one of the 
manuscripts of the King's Library at Paris, dated about 
the middle of the fifteenth century, which as he says 
nearly resembles a modern watch. The balance is thej;^ 
called " The circle fastened to the stem of the pallets, 
and moved by the force with it. In that singularly wild 
and extravagant book, entitled '' A History of both 
Worlds," by Robert Flud, are given two drawings of 
the wheel-work of the clocks and watches in use before 
the application of the pendulum. An inspection of them 
will show how little remained to be done when the 



isochronism of the pendulum was discovered. Fig^ 1 
represents ^' the large clocks moved by a weight, such as 
are put up in churches and tiyrcts : Fig, 2. the small 
ones moved by a spring, such as are worn round the 
neck, or placed on a shelf or table. The use of the 
chain is to equalize the spring, which is strongest at the 

beginning of its motion." This contrivance of the chain 
is mentioned by Cardan, in 15T0, and is probably still 
older. In both figures the name given to the cross bai', 
with the weight attached to it, is '' the time or balance, 
(tempus seu libratio) by which the motion is equalized." 



The manner in which Huyghens first applied the pendu- 
lum is shown in FigyS. The action in the old clocks 
of the balance, or rttKe as it was also called, was by check- 
ing the motion of the descending weight till its inertia was 
overcome ; it was then forced round till the opposite pal- 
er engaged in the toothed wheel. The balance was thus 
suddenly and forcibly reduced to a state of rest, and again 
set in motion in the opposite direction. It will be ob- 
served that these balances wanted the spiral spring intro- 
duced in all modern watches, which has a property of 
isochronism similar to that of the pendulum. Hooke is 
generally named as the discoverer of this property of 
springs, and as the author of its application to the im- 
provement of watches, but the inv^ention is disputed with 
him by Huyghens. Lahlre asserts, that the isochronism 
of springs was communicated to Huyghens at Paris by 
Hautefeuille, and that this was the reason why Huyghens 
failed to obtain the patent he solicited for the construc- 
tion of spring watches. A great number of curious con- 
trivances at this early period in the history of Horology, 
may be seen in Schort's Magia Naturae, pubHshed at Nu- 
remberg in 1664. 

Galileo was early convinced of the importance of liis 
pendulum to the accuracy of astronomical observations ; 
but the progress of invention is such that the steps which 
on looking back seem the easiest to make, are often those 
which are the longest delayed. Galileo recognized the 
principle of the isochronism of the pendulum, and recom- 
mended it as the measurer of time in 1 583 ; yet fifty 
years later, although constantly using it, he had not de- 
vised a more convenient method of doing so, than is con- 
tained in the following description taken from liis '' As- 
tronomical Operations." 


^' A very exact time-measurer for minute intervals of 
time, is a heavy pendulum of any size hanged by a fine 
thread, which, if removed from the perpendicular and 
allowed to swing freely, always completes its vibrations, 
be they great or small, in exactly the same time." 

The mode of finding exactly by means of this the 
quantity of any time reduced to hours, minutes, seconds, 
&c., which are the divisions commonly used among as- 
tronomers, is this :— '' Fit up a pendulum of any length, 
as for instance about a foot long, and count patiently 
(only for once) the number of vibrations during a natural 
day. Our object will be attained if we know the exact 
revolution of the natural day. The observer must then 
fix a telescope in the direction of any star, and continue 
to watch it till it disappears from the field of view. At 
that instant he must begin to count the vibrations of the 
pendulum, continuing all night and the following day till 
the return of the same star within the field of view of the 
telescope, and its second disappearance, as on the first 
night. Bearing in recollection the total number of vibra- 
tions thus made in twenty-four hours, the time corres- 
ponding to any other number of vibrations will be imme- 
diately given by the Golden rule." 

A second extract out of Galileo's Dutch correspon- 
dence, in 1637, will show the extent of his improve- 
ments at that time : — "^ I come now to the second con- 
trivance for increasing immensely the exactness of astro- 
nomical observations. I allude to my time-measurer, 
the precision of which is so great, and such that it will 
give the exact quantity of hours, minutes, seconds, and 
even thirds, if their recurrence could be counted ; and 
its constancy is such that two, four, or six such instru- 


ments will go on together so equably that one will not 
differ from another so much as the beat of a pulse, not 
only in an hour, but even in a day or a month." — '' I do 
not make use of a weight hanging by a thread, but a 
heavy and solid pendulum, made for instance of brass or 
copper, in the shape of a circulai' sector of twelve or 
fifteen degrees, the radius of which m.ay be two or three 
palms, and the greater it is the less trouble will there be 
in attending it. This sector, such as I have described, 
1 make thickest in the middle radius, tapering gradually 
towards the edges, where I terminate it in a tolerably 
sharp line, to obviate as much as possible the resistance 
of the air, which is the sole cause of its retardation." 
— [These last words deserve notice, because, in a pre- 
vious discussion, Galileo had observed that the parts of 
the pendulum nearest the point of suspension have a ten- 
dency to vibrate quicker than those at the other end, and 
seems to have thought erroneously that the stoppage of 
the pendulum is partly to be attributed to this cause.] 
— '' This is pierced in the centre, through which is pass- 
ed an iron bar shaped hke those on which steelyards 
hang, terminated below in an angle, and placed on two 
bronze supports, that they may wear away less during a 
long motion of the sector. If the sector (when accu- 
rately balanced) be removed several degrees from its 
perpendicular position, it will continue a reciprocal mo- 
tion through a very great number of vibrations before it 
will stop ; and in order that it may continue its motion 
as long as is wanted, the attendant must occasionally give 
it a smart push, to carry it back to large vibrations." 
Galileo then describes as before the method of counting 
the vibrations in the course of a day, and gives the rule 


that the lengths of two similar pendulums will have the 
same proportion as the squares of their times of vibration. 
He then continues : ''Now to save the fatigue of the 
assistant in continually counting the vibrations, this is a 
convenient contrivance : A very small and dehcate needle 
extends out from the middle of the circumference of the 
sector Vvhich in passing strikes a rod fixed at one end ; 
this rod rests upon the teeth of a wheel as light as paper, 
placed in a horizontal plane near the pendulum, having 
round it teeth cut like those of a savv, that is to say, with 
one side of eaeli tooth perpendicular to the rim of the 
wheel and the other inclined obliquely. The rod strik- 
ing against the perpendicular side of the tooth moves it, 
but as the same rod returns against the obhque side, it 
does not move in the contrary way, but slips over it and 
falls at the foot of the following tooth, so that the motion 
of the w^heel will be always in the same direction. And 
by counting the teeth you may see at will the number of 
teeth passed and consequently the number of vibrations 
and of particles of time elapsed. You may also fit to the 
axis of this first wheel a second, with a small number of 
teeth, touching another greater toothed wheel, &c. But 
it is superfluous to point out this to you, who have by you 
men very ingenious and well skilled in making clocks and 
other admirable machines ; and on this new principle, 
that the pendulum makes its great and small vibrations in 
the same time exactly, they will inventxontrivances more 
subtle than any I can suggest ; and as the error of clocks 
consists principally in the disability of workmen hitherto 
to adjust what we call the balance of the clock, so that it 
I may vibrate regularly, my very simple pendulum, which 
I is not liable to any alteration, affords a mean of main^ 



taining the measures of time always equal." The con- 
trh'ance thus described would be somewhat similar to 
the annexed representation, but it is almost certain thai 
no such instrument was actually constructed 

It must be owned that Gahleo greatly overated the ac- 
curacy of his timekeeper ; and in asserting so positively 
that wdiich he had certainly not experienced, he seems to 
depart from his own principles of philosophizing. It will 
De remarked that m this passage he still is of the errone- 
ous opinion, that all the vibrations great or small of the 
same pendulum take exactly the same time : and we 
have not been able to find any trace ofhisha\mg ever 
held aTdifferent opinion, unless perhaps in the Dialogues, 
where he says, '' If the vibrations are not exactly equal, 
they are at least insensibly different." This is very 
much at variance witli the statement in the ]Memoirs of 
the Academia del Cimento, edited by their secretary, 
Magalotti, on the credit of which Gahleo's claim to the 
pendulum-clock chiefly rests. It is there said tliat expe- 
rience shows that the smallest vibrations are radier the 
quickest, '' as Galileo announced after the observation, 
which in 15S3 he was the first to make of tlieir approx- 
imate equahty." It is not possible immediately in con- 
nexion with so glaring a mistatement, to give imphcit 


credence to the assertion in the next sentence, that '' to 
obviate this inconvenience.-'^ Galileo was the first to 
contrive a clock, constructed in 1649. by his son Vin- 
cenzo, in vrhich. by the action of a weight or spring, 
the pendulum was constrained to move always from the 
same height. Indeed it appears as if Magalotti did not 
alwavs tell this story in the same manner, for he is re- 
ferred to as the author of the account given by Becher, 
'^ that Galileo J^himself made a pendulum-clock, one of 
which was sent to Holland," plainly insinuating that 
Huyshens was a mere copyist. These two accounts 
therefore serve to invalidate each other's credibility. 
Tiraboschi asserts that, at the time he wrote, the mathe- 
matical professor at Pisa was in possession of the iden- 
tical clock constructed by Treffler under Vincenzo's di- 
rections ; and quotes a letter from Campani. to whom it 
was shown by Ferdinand. '^ old, rust}-, and unfinished as 
Gahleo's son made it before 1649.'' Viviani. on the 
other hand, says that Treffler constructed tliis same clock 
some time after Vincenzo's death, (which happened in 
1649), on a different principle fi-om Vincenzo's ideas, 
although he says distinctly that he heard Galileo describe 
an apphcation of the pendulum to a clock similar to 
Huyghens* contrivance. Campani did not actually see 
this clock till 1659, which was three years after Huyg- 
hens' invention, so that perhaps Huyghens was too easily 
satisfied when, on occasion of the answer which Ferdi- 
nand sent to his complaints of the Memorie del Cimento 
he wrote to Bouillaud. '• I must however beheve, since 
such a prince assures me, that Galileo had this idea be- 
fore me.'' 

There is another circumstance almost amountins: to a 


proof that it was an afterthought to attribute the merit of 
constructing the pendulum-clock to Galileo, for on the 
reverse of a medal struck by Viviani, and inscribed ^' to 
the memory of his excellent instructor," is a rude ex- 
hibition of the principal objects to which Galileo's atten- 
tion was directed. The pendulum is rep^'esented simply 
by a weight attached to a string hanging on ihe face of a 
rock. It is probable that, in a design expressly intended 
to commemorate Galileo's inventions, Viviani would 
have introduced the timekeeper in the most perfect form 
to which it had been brought by him. Riccioli, whose 
industry was unwearied in collecting every fact and ar- 
gument which related in any way to the astronomical and 
mechanical knowledge and opinions of his time, express- 
ly recommends swinging a pendulum, or perpendicular 
as it w^as often called (only a few years before Huyhens' 
publication), as much more accurate than any clock. 
Join to all these arguments Huyghens' positive assertion, 
that if Galileo had conceived any such idea, he at least 
was entirely ignorant of it, and no doubt can remain that 
the merit of the original invention (such as it was) rests 
entirely with Huyghens. The step indeed seems sim- 
ple enough for a less genius than his : for the property 
of the pendulum was known, and the conversion of a ro- 
tatory into a reciprocating motion was known ; but the 
connexion of the one with the other having been so long 
delayed we must suppose that difficulties existed where 
we are not now able to perceive them, for Huyghen's 
improvement was received with universal admiration. 

There may be many who will consider the penduluna 
as undeserving so long a discussion ; who do not know or 
remember that the telescope itself has hardly done more ,: 


for the precision of astronomical observations than this 
simple instrument, not to mention the invaluable conven- 
ience of an uniform and accurate timekeeper in the daily 
intercourse of life. The patience and industry of modern 
observers are often the theme of well-merited praise, but 
we must look with a still higher degree of wonder on 
such men as Tycho-Brahe and his contemporaries, who 
were driven by the want of any timekeeper on which 
they could depend to the most laborious expedients, and 
who nevertheless persevered to the best of their ability, 
undisgusted either by the tedium of such processes, or 
by the discouraging consciousness of the necessary im- 
perfection of their most approved methods, and instru- 

The invaluable regularity of the pendulum's motion 
was soon made subservient to ulterior purposes beyond 
that of merely registering time. We have seen the im- 
portant assistance it afforded in establishing the laws of 
motion ; and when the theory founded on those laws was 
extended and improved, the pendulum was again instru- 
mental, by a species of approximate reasoning famihar to 
all who are acquainted with physical inquiries, in point- 
ing out by its minute irregularities in different parts of 
the earth, a corresponding change in the weight of all 
bodies in those different situations, supposed to be the 
consequence of a greater distance from the axis of the 
earth's rotation ; since that would occasion the force 
I of attraction to be counterbalanced by an increased 
' centrifugal force. The theory which kept pace with the 
; constantly increasing accuracy of such observations, 
I proving consistent in all trials of it, has left Uttle room 
j for future doubts ; and in this manner the pendulum in 


intelligent hands became the simplest instrument for as- 
certaining the form of the globe which we inhabit. An 
Enghsh astronomer, who corresponded with Kepler un- 
der the signature of Brutius (whose real name perhaps 
might be Bruce,) had already declared his belief in 1603, 
that '' the earth on which we tread is neither round nor 
globular, but more nearly of an oval figure." There is 
nothing to guide us to the grounds on which he formed 
this opinion, which was perhaps only a lucky guess. 
Kepler V note upon it is : "^ This is not altogether to be 

A farther use of the pendulum is in furnishing a general 
and unperishing standard of measure. This apphcation 
is suggested in the third volume of the ' Reflections ' of 
Mersenne, published in 1647, where he observes that it 
may be best for the future not to divide time into hours, 
minutes, and seconds, but to express its parts by the 
number of vibrations of a pendulum of given lengths, 
swinging through a given arc. It was soon seen that it 
would be more convenient to invert this process, and to 
choose as an unit of length the pendulum which should 
make a certain number of vibrations in the unit of time, 
naturally determined by the revolution of the earth on its 
axis. Our Royal Society took an active part in these 
experiments, which seem, notwithstanding their utility, 
to have met from the first with much of the same ridicule 
which was lavished upon them by the ignorant, w^hen 
recently repeated for the same purpose. '' I contend,'' 
says Graunt in a dedication to the Royal Society, dated 
1662, ''against the envious schismatics of your society, 
(who think you do nothing except you presently trans- 
mute metals, make butter and cheese without milk, and, 


as their own ballad hath it, make leather without hides,) 
by asserting the usefulness of even all your preparatory 
and lucifeijbus experiments, being not the ceremonies, 
but the substance and principles of useful arts. For I 
find in trade the want of an universal measure, and have 
heard musicians wrangle about the just and uniform keep- 
ing of time in their consorts, and therefore cannot with 
patience hear that your labors about vibrations, eminent- 
ly conducing to both, should be slighted, nor your pen- 
dula called swing-swangs with scorn. "^ 


Character of Galileo — Miscellaneous details — his Death 
— Conclusion, 

The remaining years of Galileo's life were spent at 
Arcetri, where indeed, even if the Inquisition had grant- 
ed his liberty, his increasing age and infirmities would 

* See also Hudibras, Part II. Cant. III. 

They 're guilty by their own confessions 
Of felony, and at the Sessions 
Upon the bench, I will so handle 'em, 
That the vibration of this pendulum 
Shall make all tailors' yards of one 
Unanimous opinion ; ^ 
A thing he long has vaumpd of, 
But now shall make it out of proof. 
Hudibras was certainly written before 1663 : ten years later Huyghens 
speaks of the idea of so employing the pendulum as a common one. 


probably have detained him. The rigid caution with 
which he had been watched in Florence was in a ^reat 
measure relaxed, and he was permitted to see the friends, 
who crowded round him to express their respect and 
sympathy. The Grand Duke visited him frequently, 
and many distinguished strangers, such as Gassendi and 
Deodati, came into Italy solely for the purpose of testi- 
fying their admiration of his character. Among other 
visitors the name of Milton will be read with interest : 
we may probably refer to tlje effects of this interview the 
allusions to Galileo's discoveries, so frequently intro- 
duced into his poem. Milton mentions in his ' Areo- 
pagitica,' that he saw Galileo whilst in Italy, but enters 
into no details of his visit. 

Galileo was fond of society^, and his cheerful and popular 
manners rendered him an universal favorite among those 
who were admitted to his intimacy. Among these, Vi- 
viani, who formed one of his family during the three last 
years of his life, deserves particular notice, on account of 
the strong attachment and almost filial veneration with 
w^hich he ever regarded his master and benefactor. His 
long life, which was prolonged to the completion of his 
81st year in 1703, enabled him to see the triumphant 
. establishment of the truths on account of which Galileo 
had endured so many insults, and even in his old age, 
when in his turn he had acquired a claim to the rever- 
ence of a youno;er generation, our Royal Society, who 
invited him among them in 1696, felt that the compli- 
mentary language in which they addressed him as the 
first mathematician of the age w^ould have been incom- 
plete and unsatisfactory without an allusion to the friend- 


ship that gained him the cherished title of '' The last 
pupil of Galileo."* 

Torricelli, another of Gahleo's most celebrated follow- 
ers, became a member of his family in October, 1641 : 
he first learned mathematics from Castelli, and occasion- 
ally lectured for him at Rome, in which manner he was 
employed when Galileo, who had seen his book ' On 
Motion,' and augured the greatest success from such a 
beginning, invited him to his house — an ofier which Tor- 
ricelH eagerly embraced, although he enjoyed the ad- 
vantages of it but for a short time. He afterwards suc- 
ceeded Galileo in his situation at the court of Florence,! 
but survived him only a few years. 

It is from the accounts of Viviani and Gherardini that 
we principally draw the following particulars of Galileo's 
person and character : — Signor Galileo was of a cheerful 
and pleasant countenance, especially in his old age, 
squai'e built, and well proportioned in stature, and rather 
above the middle size. His complexion was fair and 
sanguine, his eyes brilliant, and his hair of a reddish 
cast. His constitution was naturally strong, but worn 
out by fatigue of mind and body, so as frequently to be 
reduced to a state of the utmost weakness. He was sub- 
ject to attacks of hypochondria, and often m.olested by 
severe and dangerous illnesses, occasioned in great meas- 

* The words of his diploma are : Galilsei in mathematicis disciplinis dis- 
cipulus, in serumnis socius. Italicum ingenium ita perpolivit optimis artibus Ht 
inter mathematicos sseculi nostri facile princeps per orbera litterarium nume- 
retur . — Tiraboschi . 

t On this occasion the taste of the time showed itself in the following an* 
agram ] 

Evangelista Torricellieus, 
En yirescit Galilseus alter. 


ure by his sleepless nights, the whole of which he ire- I 
quently spent in astronomical observations. During up- J 
wards of forty-eight years of his hfe, he was tormented 
with acute rheumatic pains, suffering particularly on any \ 
change of weather. He found himself most free from ! 
these pains whilst residing in the country, of which con- | 
sequently he became very fond : besides, he used to say | 
that in the country he had greater freedom to read the 
book of Nature, which lay there open before him. His 
Hbrary was very small, but well chosen, and open to the 
use of the friends whom he loved to see assembled round 
him, and whom he was accustomed to receive in the | 
most hospitable manner. He ate sparingly himself; but ^ 
was particularly choice in the selection of his wines, ' 
which in the latter part of his life were regularly supplied 
out of the Grand Duke's cellars. This taste gave an ' 
additional stimulus to his agricultural pursuits, and many ! 
of his leisure hours were spent in the cultivation and < 
superintendence of his vineyards. It should seem I 
that he was considered a good judge of wine ; for Vivi- | 
ani has preserved one of his receipts in a collection of ; 
miscellaneous experiments. In it he strongly recom- J 
mends that for wine of the first quahty, that juice only 
should be employed, which is pressed out by the mere 
weight of the heaped grapes, which would probably be 
that of the ripest fruit. The following letter, written 
in his 74th year, is dated, "^ From my prison at Arce- i 
tri. — I am forced to avail myself of your assistance and ^ 
favor, agreeably to your obliging offers, in consequence of i 
the excessive chill of the weather, and of old age, and I 
from having drained out my grand stock of a hundred 3 
feottles, which I laid in two years ago ; not to mention ' 


some minor particulars during the last two months, which 
I received from my Serene Master, the Most Eminent 
Lord Cardinal, their Highnesses the Princes, and the 
Most Excellent Duke of Guise, besides cleaning out two 
barrels of the wine of this country. Now, I beg that 
with all due diligence and industry, and with considera- 
tion, and in taking counsel widi the most refined palates:, 
you willfprovide me with two cases, that is to say, with 
forty flasks of different wines, the most exquisite that 
you can find ; take no thought of the expense, because I 
stint myself so much in all other pleasures that I can af- 
ford to lay out something at the request of Bacchus, with- 
out giving offence to his two companions Ceres and 
Venus. You must be careful to leave out neither Scilk> 
nor Carino (I believe they meant to call them Scylla and 
Charybdis,) nor the country of my master, Archimedes 
of Syracuse, nor Greek wines, nor clarets, &c. &c. 
The expense I shall easily be able to satisfy, but not 
the infinite obligation." 

In his expenditure Galileo observed a just mean be- 
tween avarice and profusion : he spared no cost necessa- 
ry for the success of his many and various experiments, and 
spent krge sums in charity and hospitality and in assisdng 
those in w^hom he discovered excellence in any art or pro- 
fession, many of whom he maintained in his own house. 
His temper was easily ruffled, but still more easily pacifi- 
-ed. He seldom conversed on mathematical or philosophi- 
\ cal topics except among his intimate friends ; and when 
such subjects were abruptly brought before him, as was 
often the case by the numberless visitors he was in the 
habit of receiving, he showed great readiness in turning 
the- conversation into more popular channels, in such 


manner however that he often contrived to introduce 
something to satisfy the curiosity of the inquirers. His 
memory was uncommonly tenacious, and stored with a 
vast variety of old songs and stories, which he was in the 
constant habit of quoting and alluding to. His favorite 
Italian authors were Aiiosto, Petrarca, and Berni, great 
part of whose poems he was able to repeat. His ex- 
cessive admiration of Ariosto determined the side which 
he took against Tasso in the virulent and unnecessary 
controversy which has divided Italy so long on the res- 
pective merits of these two great poets ; and he was accus- 
tomed to say that reading Tasso after Ariosto was like 
tasting cucumbers after melons. When quite a youth, 
he wrote a great number of critical remarks on Tasso's 
Gerusalemme Liberata, w'hich one of his friends bor- 
rowed, and forgot to return. For a long time it w^as 
thought that the manuscript had perished, till the Abbe 
Serassi discovered it, whilst collecting materials for 
his Life of Tasso, published at Rome in 1785. Se- 
rassi being a violent partizan of Tasso, but also unwilling 
to lose the credit of the discovery, copied the manuscript, 
but w^ithout any intention of pubhshing it, '^ till he could 
find leism-e for replying properly to the sophistical and 
unfounded attacks of a critic so celebrated on other ac- 
counts." He announced liis discovery as having been 
made '^in one of the famous libraries at Rome," w^hich 
vague indication he with some reason considered insuf- 
ficient to lead to a second discovery. On Serasis's 
death, his copy was found containing a reference to the 
situation of the original ; the criticisms were published, 
and form the greatest part of the last volume of the Milan 
edition of Galileo's works. The manuscript was iraperr 


feet at the time of this second discovery, several leaves 
having been torn out, it is not knowni by whom. 

The opinion of the most judicious Italian critics ap- 
pears to be, that it would have been more for Gah- 
leo's credit if these remarks had never been made public : 
they are written in a spirit of flippant violence, such as 
might not be extraordinary in a common juvenile critic, 
but which it is painful to notice from the pen of Gahleo. 

Two or three sonnets are extant, written by Galileo 
himself, and in two instances he has not scrupled to ap- 
propriate the conceits of the poet he affected to undervalue. 
It should be mentioned that Galileo's matured taste rather 
receded from the violence of his early prejudices, for at 
a later period of his hfe he used to shun comparing the 
two ; and when forced to give an opinion he said, "^ that 
Tasso's appeared the finer poem, but that Ariosto gave 
him the greater pleasure." Besides these sonnets, there 
is extant a short burlpsque poem written by him, ''In 
abuse of Gowns," when on his first becoming Professor 
at Pisa, he found himself obliged by custom to wear his 
professional habit in ever}'- company. It is written not 
without humor, but does not bear comparison with Ber- 
ni whom he imitated. 

There are several detached subjects treated of by Ga- 
lileo, which may be noticed in this place. A letter by 
him containing the solution of a problem in Chances is 
probably the earliest notice extant of the application of 
mathematics to that interesting subject : the correspond- 
ence between Pascal and Fermat, with which its history 
is generally made to begin, not having taken place till at 
least twelve years later. There can be litde doubt after 
the clear account of Carlo Dati, that Gahleo was the 


first to examine the curve called the Cycloid, described 
by a point in the rim of a wheel rolling on in a straight 
line, which he recommended as a graceful form for the 
arch of a bridge at Pisa. He even divined that the area 
contained between it and its base is exactly three times 
that of the generating circle. He seems to have been 
unable to verify this guess by strict geometrical reason- 
ing, for Viviani tells an odd story, that in order to satis- 
fy his doubts he cut out several large cycloids of paste- 
board, but finding the weight in every trial to be rather 
less than three times that of the circle, he suspected 
the proportion to be irrational, and that there was some 
error in his estimation ; the inquiry he abandoned w^as 
afterwards resumed with suc€ess by his pupil TorricelH. 

The account which Lagalla gives of an experiment 
shown in his presence by Galileo carries the observation 
of the phosphorescence of the Bologna stone at least as 
far back asl612. Other writers mention the name of an 
alchymist, who according to them discovered it accident- 
ally in 1603. Cesi, Lagalla, and one or two others, 
had passed the night at Galileo's house with the intention 
of observing Venus and Saturn ; but the night being 
cloudy, the conversation turned on other matters, and 
especially on the nature of fight, '' on which Galileo took 
a smafi wooden box at daybreak before sunrise, and 
showed us some small stones in it, desiring us to ob- 
serve that they were not in the least degree kmiinous. 
Having then exposed them for some time to the twilight 
he shut the window again ; and in the midst of the dark 
room showed us the stones, shining and glistening with a 
faint light, which we saw presently decay and become ex- 
tinguished. " In 1640, Liceti attempted to refer the effect 


of the earthshine upon the moon to a similar phosphores- 
ent quality of that luminary, to which Galileo, then aged 
76, replied by a long and able letter, enforcing the true 
explanation he had formerly given. 

Although quite blind., and nearly deaf, the intellectual 
powers of Galileo remained to the end of his life ; but 
he occasinally felt that he was overworking himself, and 
used to complain to his friend Micanzio that he found 
his head too busy for his body. ''I cannot keep my 
restless brain from grinding on, although with great loss 
of time ; for whatever idea comes into my head with re- 
spect to any novelty, drives out of it whatever I had been 
thinking of just before." He was busily engaged in con- 
sidering the natui'e of the force of percussion, and Tor- 
ricelh was employed in arranging his investigations for a 
continuation of the ^ Dialogues on Motion,' when he was 
seized with an attack of fever and palpitation of the heart, 
which, after an illness of two months, put an end to his 
long, laborious, and useful life, on the 8th of January, 
.1642, just one year before his great successor Newton 
was born. 

The mahce of his enemies was scarcely allayed by 
his death. His right of making a will was disputed, as 
having died a prisoner to the Inquisition, as well as his 
right to burial in consecrated ground. These were at 
last conceded, but Urban anxiously interfered to prevent 
the design of erecting a monument to him in the church 
of Sante Croce, in Florence, for which a large sum had 
been subscribed. His body was accordingly buried in 
an obscure corner of the church, which for upwards of 
thirty years after his death was unmarked even by an in- 
scription to his memory. It was not till a century later 


that tlie splendid monument was erected which now cov- 
ers his and Viviani's remains. When their bodies were 
disinterred in 1737 for the purpose of being removed to 
their new restingplace, Capponi, the president of the 
Florentine Academy, in a spirit of spurious admiration, 
mutilated Galileo's body, by removing the thumb and fore- 
finger of the right hand, and one of the vertebras of the 
back, which are still preserved in some of the Italian 
museums. The monument was put up at the expense 
of his biographer, Nelli, to whom Viviani's property de- 
scended, charged wtth the condition of erecting it. Nor 
was this the only public testimony w^hich Viviani gave of 
his attachment. The medal which he struck in honor 
of Gahleo has already been mentioned ; he also, as soon 
as it was safe to do so, covered every side of the house 
in which he hved with laudatory inscriptions to the same 
effect. A bust of Galileo was placed over the door, 
and two bas-reliefs on each side, representing some of 
his principal discoveries. Not less than five other med- 
als were struck in honor of him during his residence at 
Padua and Florence, which are all engraved in Venturi's 

There are several good portraits of Galileo extant, 
two of which by Titi and Subtermanns, are engraved in 
NeUi's Life of Gahleo. Another by Subtermanns is in 
the Florentine Gallery, and an engraving from a copy of 
this is given by Venturi. There is also a very fine en- 
graving from the original picture. An engraving from 
another original picture is in the frontispiece of the Pa- 
dua edition of his works. Salisbury seems in the follow- 
ing passage to describe a portrait of Galileo painted by 
himself: ''He did not contemn the other inferior arts, 


for he had a good hand in sculpture and carving ; but 
his particular care was to paint well. By the pencil he 
described what his telescope discovered ; in one he ex- 
ceeded art, in the other, nature. Osorius, the eloquent 
bishop of Sylva, esteems one piece of Mendoza the wise 
Spanish minister's felicity, to have been this, that he was 
contemporary to Titian, and that by his hand he w^as 
drawn in a fair tablet. And Galilaeus, lest he should 
want the same good fortune, made so good a progress in 
this curious art, that he became his own Buonarota ; 
and because there w as no other copy worthy of his pen- 
cil, drew himself." No other author makes the shghtest 
allusion to such a painting ; and it appears more likely 
that Salusbury should be mistaken than that so interest- 
ing a portrait should have been entirely lost sight of. 

Galileo's house at Arcetri was standing in 1821, w^hen 
Venturi visited it, and found it in the same state in which 
Galileo might be supposed to have left it. It is situated 
nearly a mile from Florence, on the south-eastern side, 
and about a gun-shot to the northw^est of the convent of 
St. Matthew. Nelli placed a suitable inscription over 
the door of the house, which belonged in 1821 to a Sig- 
ner Ahmari. 

Although Nelli's Life of Galileo disappointed the ex- 
pectations that had been formed of it, it is impossible 
for any admirer of Galileo not to feel the greatest degree 
of gratitude towards him, for the successful activity with 
which he rescued so many records of the illustrious phi- 
losopher from destruction. After Galileo's death, the 
orincipal part of his books, manuscripts, and instruments 
were put into the charge of Viviani, who was himself at 
that time an object of great suspicion ; most of them he 

A A 


thought it prudent to conceal, till the superstitious out- 
cries against Galileo should be silenced. At Viviani's 
death, he left his library, containing a very complete 
collection of the works of all the mathematicians who 
had preceded him (and amongst them those of Galileo, 
Torricelli, and Castelli, all which were enriched with 
notes and additions by himself), to the hospital of St, 
Mary at Florence, where an extensive library already 
existed. The directors of the hospital sold this unique 
collection in 1781, when it became entirely dispersed. 
The manuscripts in Viviani's possession passed to his 
nephew, the Abbe Panzanini, together with the portraits 
of the chief personages of the Galilean school, Galileo's 
instruments, and, among other curiosities, the emerald 
ring which he wore as a member of the Lyncean Acad- 
emy. A great nmp.ber of these books and manuscripts 
were purchased at different times by Nelli, after the 
death of Panzanini, from his relations, who were igno- 
rant or regardless of their value. One of his chief acqui- 
sitions was made by an extraordinary accident, related by 
Tozzetti with the following details, which we repeat, as 
they seem to authenticate the story : — '' In the spring of 
1739, the famous Doctor Lami went out according to 
his custom to breakfast whh some of his friends at the 
Inn of the Bridge by the starting place ; and as he and 
Sig. Nelh were passing through the market, it occurred 
to them to buy some Bologna sausages from the pork- 
butcher, Cioci, who was supposed to excel in making 
them. They went into the shop, had their sausages cut 
off and rolled in paper, which Nelh put into his hat. On 
reaching the inn, and calling for a plate to put them in, 
Nelli observed that the paper in which they had been 


rolled was one of Gallileo's letters. He cleaned it as 
well as he could with his napkin, and put it into his pock- 
et without savin2: a word to Lami ; and as soon as he 
returned into the city and could get clear of him, 
he flew to the shop of Cioci, who told him that a ser- 
vant, whom he did not know, brought him from 
time to time similar letters, which he bought by 
weight as waste paper. NeUi bought all that remained, 
and on the servant's next reappearance in a few days, 
he learned the quarter whence they came, and after 
some time succeeded at a small expense in getting into 
his own possession an old corn-chest, containing all that 
still remained of the precious treasures which Yiviani had 
concealed in it ninety years before. " 

The earhest biographical notice of Galileo is th^it in 
the Obituary of the Mercurio Itahco, published at Venice 
in 1647, by Vittorio Siri It is very short, but contains 
an exact enumeration of his principal works and discov 
eries. Rossi, wdio wrote under the name of Janus N'c 
iu3 Erythrseus, introduced an account of Galileo in hie 
Pinacotheca Imaginem Illustrium, in which the story c 
his illegitimacy first made its appearance. In 1664^ Sal 
usbury published a life of Galileo in the second volume 
of his mathematical Collections, the greater part of which 
is a translation of Galileo's principal works. Almost the 
whole edition of the second volume of Salusbury's book 
was burnt in the great fire of London. ChaufFepie says 
that only one copy is known to be extant in England: 
this is now in the well-known library of the earl of Mac- 
clesfield, to whose kindness the author is much indebted 
for the use he has been allowed to make of this unique 
volume. A fra2;ment of this second volume is in the 


Bodleian library at Oxford. The translations in the pre- 
ceding pages are mostly founded upon Salusbury's ver- 
sion. Salusbury's account, althougli that of an enthusi- 
astic admirer of Galileo, is too p\olix to be interesting : 
the general style of the performance may be guessed 
from the title of the first chapter — ' Of man in general, 
and how he excelleih all the other Animals.' After in- 
forming his readers that Galileo was born at Pisa, he 
proceeds : — '' Italy is affirmed to have been the first 
that peopled the world after the universal deluge, being 
governed by Janus, Cameses, Saturn, &c." His de- 
scription of Galileo's childhood is somewhat quaint. 
^' Before others had left making of dirt pyes, he wa.«^ fra- 
ming of diagrams ; and whilst others w^ere whipping of 
toppes, he was considering the cause of their motion. " 
It is on the whole tolerably correct, especially if we take 
into account that Salusbury had not yet seen Yiviani's 
Life, though composed some yeai's earlier. 

The Life of Galileo by Viviani was first written as an 
outline of an intended larger work, but this latter was 
never completed. This sketch was published in the 
Memoirs of the Florentine Academy, of which Galileo 
had been one of the annual presidents, and afterwards 
prefixed to the complete editions of Galileo's v/orks ; it 
is written in a very agreeable and flowing style, and has 
beea the groundwork of most subsequent accounts. An- 
other original memoir by Niccolo Gherardini, was pub- 
lished by Tozzetti. A great number of references to au- 
thors who have treated of Galileo is given by Sach in his 
Onomasticon. An approved Latin memoir by Brenna 
is in the first volume of Fabroni's Vitas Italorum lUustri- 
urn ; he has however fallen into several errors : this same 


work contains the liv^es of several o{ bis principal follow- 

The article in Chauffepie's Continuation of Bayle's 
Dictionary does not contain any thing which is not in the 
earlier accounts. 

Andres wrote an essay entitled ' Saggio sulla Filosofia 
del Galileo,' pubhshed at Mantua 1776 ; and Jagemann 
pubhshed his ' Geschichte des Leben des Galileo ' at 
Leipzig, in 1787 ; neither of these the author has been 
able to meet with. An analysis of the latter may be 
seen in Kastner's ' Geschichte des Mathematik, Gottin- 
gen, 1800,' from which it does not appear to contain any 
additional details. The 'Elogio del Galileo' by Paolo 
Frisi, first pubhshed at Leghorn in 1775, is, as its title 
expresses, rather in the nature of a panegyric than of a 
continous biographical account. It is written with very 
great elegance and intimate knowledge of the subjects of 
which it treats. Nelli gave several curious particulars 
with respect to Gahleo in his 'Saggo di Storia Letteraria 
Fiorentina, Lucca, 1759, and in 1793 published his large 
work entitled, Vita e Commercio Letterario di Gahleo 
Galilei. So uninteresting a book was probably never writ- 
ten from such excellent materials. Two thick quarto vo- 
lumes are filled with repetitions of the accounts that were 
already in print, the bulky preparation .of which com- 
pelled the author to forego the publication of the vast col- 
lection of original documents which his unwearied Zealand 
industry had collected. This defect has been in a great 
measure supplied by Venturi in 1818 and 1821, who has 
not only incorporated in his work many of Nelli 's manu- 
scripts, but has brought together a number of scattered no- 
tices of Galileo and his writings from a variety of outlying 


sources — a service which the writer is able to appreciate 
from having gone through die greatest part of the same la- 
bor before he was fortunate enough to meet w'ith Venturi's 
book. Still there are many letters cited by Nelli, which 
do not appear either in his book or Venturi's. Carlo 
Dati, in 1663, quotes '' the registers of Galileo's cor- 
respondence arranged in alphabetical order, in ten large 
volumes." The writer has no means of ascertaining what 
collection this may have been ; it is difficult to suppose 
that one so arranged should have been lost sight of. It is 
understood tliat a life of Gahleo is preparing at this mo- 
ment in Florence, by desire of the present Grand Duke, 
which will probably throw much additional light on the 
character and merits of this great and useful philosopher. 

The first editions of his various treatises, as men- 
tioned by Nelli, are given below. Clement, in his 
* Bibliotheque Curieuse,' has pointed out such among 
them, and the many others which have been printed, as 
bave become rare. 

The Florentine edition is the one used by the Acade- 
mia della Crusca for their references ; for which reason 
Its paging is marked in the margin of the edition of Pa- 
dua, w^hich is much more complete, and is the one which 
has been on the present occasion principally consulted. 

The latter contains the Dialogue on the System, which 
was not suffered to be printed in the former editions. 
The first twelve volumes of the last edition of Milan are 
a mere transcript of that of Padua: the thirteenth conatins 
in addition the letter to the Grand Duchess, the Com- 
mentary on Tasso, with some minor pieces A com- 
plete edition is still wanted, embodying all the recently dis- 
covered documents, and omitting the verbose commenta- 



ries, which, however useful when they were written, now 
convey little information that cannot be more agreeably 
and more profitably learned in treatises of a later date. 
Such was the life, and such were the pursuits of this - 
extraordinary man. The numberless inventions of his 
acute industry ; the use of the telescope, and the bril- 
liant discoveries to which it led ; the patient investigation 
of the laws of weight and motion ; must all be looked 
upon as forming but a part of his real merits, as merely 
particular demonstrations of the spirit in which he every 
where withstood the despotism of ignorance, and appeal- 
ed boldly from traditional opinions to the judgments of 
reason and common sense. He claimed and bequeathed 
to us the right of exercising our faculties in examining 
the beautiful creation which surrounds us. Idolized by his 
friends, he deserved their affection by numberless acts 
of kindness ; by his good humor, his affability, and by 
the benevolent generosity with which he devoted himself 
and a great part of his hmited income to advance their 
talents and fortunes. If an intense desire of being use- 
ful is everywhere worthy of honor ; if its value is im- 
measurably increased when united to a genius of the high- 
est order ; if we feel for one who, notwithstanding such 
titles to regard is harassed by cruel persecution, — then 
none deserve our sympathy, our admiration, and our 
gratitude, more than Galileo. 


LIST OF Galileo's works. 

Le Operazioni del Compasso Geom. e xMilit. - Padova, 1606. Fo!. 
Difesa di Gal, Galilei cotitr. all. cal. et impost, di 

Bald. Capia - . . . Venezza, 1607. 4to. 

Sydereus Nuncius - - - Venetiis, 1610. 4to, 

Discorso int. alle cose che stanno in su 1' Acqua - Firenze. 1612. 4to. 
Novantiqua SS. PP. Doctrina de S. Scripturae Tes- 

timoniis - - . Argent, 1612, 4to. 

Istovia e Demostr. int. alle Macchie Solari - Roma, 1613, 4to. 
Risp. alle oppos. del S. Lod. delle Colombe e del S. 

Vine, di Grazia - - - - Firenze, I6I5. 4to» 

Discorso delle Comete di Mario Guiducci - Firenze, 1619. 4to. 

Dialogo sopra i due Massimi Sistemi del Mondo - Firenze, 1632. 4to. 

Eiscorso e Demostr. intorno alle due nuove Scienze Leida, 1638. 4to 

Delia Scienza Meccanica - - Ravenna, 1649. 4to. 

Trattato della Sfera - . . _ Roma, 1655. 4to. 
Discorso sopra il Flusso e Refliisso' ( Scienze Fisiche 

di Tozzetti.) - - - Firenze, 1780. 4to. 

Considerazioni sul Tasso - - Roma, 1793. 

Trattato della Fortificazione. (Memorie di Venturi.) Modena, 1818. 4to. 

The editions of his collected works (in which is contained much that was 
never published separately) are — 

Opere di Gal. Galilei Line. Nob. Fior. &c. 
Opere di Gal. Galilei, Nob. Eior. Accad. 

Bologna, 1656 2 vols, 4to. 

Line. &c. 
Opere di Gal. Galilei 
Opere di Gal. Galilei 

Firenze, 1718. 3 vols. 4to. 
Padova, 1744. 4 vols. 4to. 
M4Iano, 1811. 13 vols. 8vo. 



LBTe '06 


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